ECM Eater
03-15-12, 06:25 AM
#32
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Update:
I picked up the two ECMs from the mechanic working on the LS400. As a background, the oldest one was bought refurbished and then repaired under warranty. The newest one was bought from a salvage yard. I took both to an electrical engineer at my work that designs circuit boards. He checked out the FET’s on both ECMs and did not see anything obviously wrong, although he admitted that it was hard for him to check more thoroughly without a schematic.
I settled up with the mechanic, connected the battery and newest ECM, started the car and took it for a spin.
Smoke was billowing from the exhaust and there was very little power. I let off on the gas a let the car limp along for a couple of miles with a police car behind me scrutinizing the air pollution. Drove it through town and eventually onto the interstate. Above 2000 RPMs with the gas pedal pushed half way down, the engine would miss or stall. Releasing the gas pedal allowed the engine to resume running. As time passed it seemed to perform better. After about 15 miles I could press the gas to the floor and had good acceleration. I said to myself, hey, maybe it’s fixed. Was the ECM in the learning phase and establishing new performance parameters? Perhaps the older ECM was OK too. So, I stopped, changed to the older EMC, started the engine and drove on down the road. That was probably a mistake.
The performance was horrible. The idle speed fluctuated between 1200 and 1500 RPM and cycled between these two RPMs every second. The car seemed to be in limp mode. Again, pressing the accelerator past half way resulted in the engine stalling and the CEL turning on. Releasing the gas pedal allowed the engine to run and turned off the CEL. I drove it about 10 miles and nothing improved. So, I reinstalled the newer ECM.
Well, the car limped all the way home, about ten miles and it went back to the previous performance – same previous symptoms. I said to myself: I should have quit while I was ahead! Why didn’t I leave well enough alone!
When I get off work today I will take it out again and check the codes (never have done that on a Lexus – shouldn’t be too hard) and will report any updates. This could become a career!
Thanks in advance for any thoughts.
I picked up the two ECMs from the mechanic working on the LS400. As a background, the oldest one was bought refurbished and then repaired under warranty. The newest one was bought from a salvage yard. I took both to an electrical engineer at my work that designs circuit boards. He checked out the FET’s on both ECMs and did not see anything obviously wrong, although he admitted that it was hard for him to check more thoroughly without a schematic.
I settled up with the mechanic, connected the battery and newest ECM, started the car and took it for a spin.
Smoke was billowing from the exhaust and there was very little power. I let off on the gas a let the car limp along for a couple of miles with a police car behind me scrutinizing the air pollution. Drove it through town and eventually onto the interstate. Above 2000 RPMs with the gas pedal pushed half way down, the engine would miss or stall. Releasing the gas pedal allowed the engine to resume running. As time passed it seemed to perform better. After about 15 miles I could press the gas to the floor and had good acceleration. I said to myself, hey, maybe it’s fixed. Was the ECM in the learning phase and establishing new performance parameters? Perhaps the older ECM was OK too. So, I stopped, changed to the older EMC, started the engine and drove on down the road. That was probably a mistake.
The performance was horrible. The idle speed fluctuated between 1200 and 1500 RPM and cycled between these two RPMs every second. The car seemed to be in limp mode. Again, pressing the accelerator past half way resulted in the engine stalling and the CEL turning on. Releasing the gas pedal allowed the engine to run and turned off the CEL. I drove it about 10 miles and nothing improved. So, I reinstalled the newer ECM.
Well, the car limped all the way home, about ten miles and it went back to the previous performance – same previous symptoms. I said to myself: I should have quit while I was ahead! Why didn’t I leave well enough alone!
When I get off work today I will take it out again and check the codes (never have done that on a Lexus – shouldn’t be too hard) and will report any updates. This could become a career!
Thanks in advance for any thoughts.
03-16-12, 07:15 AM
#34
It can have a 4 cylinders problem (running on half of the engine). Ways to find out: if you done a tune up not to long ago, on the drive side check all four spark plugs if 2 black and 2 look new that's your problem. You can run the car to it warm up give gas and see if one the catalytic converter turn red. That my problem, I just found out, I did searching and about 5 others have that problem. Thats probably why you have the lack in power. Check it out.
03-22-12, 04:33 PM
#35
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The independent auto repair shop checked the coils and found them ok. I then took the car to the Lexus dealer to ask if a top mechanic could troubleshoot the problem. The service department stated that the problem is most probably a short in the wiring harness. This was a no-cost prognosis and I appreciate that the dealer didn’t waste my money – just wish the visit resulted in something more definitive.
I did a search for how to troubleshoot a wiring short to no avail. Anyone have a systematic way to do that?
I did a search for how to troubleshoot a wiring short to no avail. Anyone have a systematic way to do that?
03-22-12, 11:33 PM
#37
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I just have checked a Japanese version of UCF20/21 service manual and found actual items / parts to be checked in accordance with the code. I don't know this fully covers UCF10/11 but I hope this is somewhat convenient for your further investigation. The original was written in Japanese and I dare translated it.
Code- Items / parts to be checked
13- Crank position sensor, cable and connector (NE Signal line), ECM
25- Spark plug, Ignition coil, Vacuum sensor, cable and connector (O2 sensor line), Injector, Fuel pressure, ECM
41- Cable and connector (Throttle sensor line), Throttle position sensor, ECM
Code- Items / parts to be checked
13- Crank position sensor, cable and connector (NE Signal line), ECM
25- Spark plug, Ignition coil, Vacuum sensor, cable and connector (O2 sensor line), Injector, Fuel pressure, ECM
41- Cable and connector (Throttle sensor line), Throttle position sensor, ECM
03-31-12, 05:32 PM
#38
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Progress Report:
Took the car to dealer. Based on the symptoms I reported and my desire to limit cost to two hours diagnostics, the mechanic suggested that the problem is most likely in the wiring harness. No diagnostics, no conclusion, no charge.
Talked to a gentleman at an ECM repair specialty shop in SC. He suggested the shop in FL that previously repaired the ECM does shoddy work – so I gave him a try. He reported that the ECM checked out OK. Again, no charge.= and my money refunded.
Bought two days of access to technical information at www. techinfo.lexus.com and downloaded the repair manual and other documents. Very extensive info for $15.
Troubleshooting procedures, as follows (hope the HOA doesn’t catch me):
Reset and checked codes. Received DTC 13. Checked resistance on the two camshaft position sensors and the crankshaft position sensor. All had resistance within specs. No shorts between wiring to the sensors. Did not check continuity on circuits (to-do).
Checked ignition wiring. The wire from the No. 2 coil to the distributor had the insulation burned through and the plastic tray below it was also burned through. I replaced all the spark plug wiring.
Disconnect the high−tension cord from the distributor and checked for spark. The No. 2 igniter circuit (passenger side) had a strong spark. The No. 1 (driver side) did not have a spark.
Checked No. 1 coil resistance on primary and secondary, and the resistance checked out within spec.
Question: Why is it that when I disconnect the high-tension wire from the No. 1 circuit the engine will not run; but it will run when I connect the wire? If I disconnect No. 2 it still runs (but that is the circuit that sparks)! Confusing?
In the effort to find out why No.1 circuit does not spark, I checked voltage check voltage between respective ECM terminals and body ground. Then checked between No.1 igniter connectors and body ground. Both were within specs. Did not check continuity in circuits – TBD.
I wish I had a conclusion to report. When (if) this is resolved, I’ll post more information.
Took the car to dealer. Based on the symptoms I reported and my desire to limit cost to two hours diagnostics, the mechanic suggested that the problem is most likely in the wiring harness. No diagnostics, no conclusion, no charge.
Talked to a gentleman at an ECM repair specialty shop in SC. He suggested the shop in FL that previously repaired the ECM does shoddy work – so I gave him a try. He reported that the ECM checked out OK. Again, no charge.= and my money refunded.
Bought two days of access to technical information at www. techinfo.lexus.com and downloaded the repair manual and other documents. Very extensive info for $15.
Troubleshooting procedures, as follows (hope the HOA doesn’t catch me):
Reset and checked codes. Received DTC 13. Checked resistance on the two camshaft position sensors and the crankshaft position sensor. All had resistance within specs. No shorts between wiring to the sensors. Did not check continuity on circuits (to-do).
Checked ignition wiring. The wire from the No. 2 coil to the distributor had the insulation burned through and the plastic tray below it was also burned through. I replaced all the spark plug wiring.
Disconnect the high−tension cord from the distributor and checked for spark. The No. 2 igniter circuit (passenger side) had a strong spark. The No. 1 (driver side) did not have a spark.
Checked No. 1 coil resistance on primary and secondary, and the resistance checked out within spec.
Question: Why is it that when I disconnect the high-tension wire from the No. 1 circuit the engine will not run; but it will run when I connect the wire? If I disconnect No. 2 it still runs (but that is the circuit that sparks)! Confusing?
In the effort to find out why No.1 circuit does not spark, I checked voltage check voltage between respective ECM terminals and body ground. Then checked between No.1 igniter connectors and body ground. Both were within specs. Did not check continuity in circuits – TBD.
I wish I had a conclusion to report. When (if) this is resolved, I’ll post more information.
03-31-12, 09:57 PM
#39
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Hi tbradford.
I have been anxious to know your progress. You already have found many and there only needs one item I write below.
Ignition coils can not be fully checked by an ohm meter. Of course the resistance is one of the important issues but the withstand voltage of the secondary winding is another very important issue. A simple ohm meter only applies 1.5V or 3V to the coil and it is impossible to check the ignition coil fully. You need to use a special equipment to check the actual withstand voltage. The simple method to check the ignition coil is to observe an actual spark at a gap of at least 10mm in the air (under 1atm). Since you have already confirmed this checking the strength of the spark. I think the spark is happening at inside of the coil. I mean the spark is happening between the layers of the windings.
Connecting the high-tension wire to the coil adds the load to it and the internal spark is not caused as is done without the high-tension wire. This must be related to the situation you are questioning the symptoms.
Anyway the next step you'd better try would be to use a good ignition coil instead of your coil No.1.
I hope you understand my limited English explanations. If you are not clear enough about my explanation, ask me again.
.
Hope your problem will be fixed soon.
Yamae
I have been anxious to know your progress. You already have found many and there only needs one item I write below.
Ignition coils can not be fully checked by an ohm meter. Of course the resistance is one of the important issues but the withstand voltage of the secondary winding is another very important issue. A simple ohm meter only applies 1.5V or 3V to the coil and it is impossible to check the ignition coil fully. You need to use a special equipment to check the actual withstand voltage. The simple method to check the ignition coil is to observe an actual spark at a gap of at least 10mm in the air (under 1atm). Since you have already confirmed this checking the strength of the spark. I think the spark is happening at inside of the coil. I mean the spark is happening between the layers of the windings.
Connecting the high-tension wire to the coil adds the load to it and the internal spark is not caused as is done without the high-tension wire. This must be related to the situation you are questioning the symptoms.
Anyway the next step you'd better try would be to use a good ignition coil instead of your coil No.1.
I hope you understand my limited English explanations. If you are not clear enough about my explanation, ask me again.
.
Hope your problem will be fixed soon.
Yamae
Last edited by Yamae; 03-31-12 at 10:01 PM.
05-18-12, 06:51 PM
#40
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Since my last update I’ve worked on and discovered the following:
Continued to have codes 13 and 41.
Performed general engine troubleshooting:
Disconnected high-tension cord from right-side distributor. No spark from wire to ground. Found the insulation on the wire was burned through. Replaced all ignition wires.
Still no spark. Resistance of ignition coil primary and secondary OK. Voltage to coil and igniter OK. Harness OK. Replaced igniter.
Spark OK. Engine ran very rough.
Checked resistance of crankshaft position sensor and two cam shaft position sensors. Checked harness for opens and shorts.
Checked cam pulley position with crank at TDC. Lo and behold the right cam pulley was off two teeth. I called the dealer that installed the belt last summer (1K miles away) and the service manager there suggested I take the car to a local dealer and he would make it right if it was a workmanship problem. The local dealer found that it was not a workmanship problem. The insides of the right distributer had “exploded” and these parts created added friction, causing the belt to jump two teeth. The mechanic replaced the two distributer rotors and also replaced the right ignition coil, water thermostat and battery. Ouch.
The engine still ran poorly as I headed home from the dealer. I asked myself, what can I do now? Is it the ECM? Is it the wiring? I was still getting codes 13 & 41. It was time to troubleshoot the Throttle Position Sensor.
The TPS had the right resistance at the sensor and at the ECM. At idle and WOT, the voltage at the TPS and ECM did not fall within the specified range. I noticed a burn mark in the TPS connector and changed the connector and TPS. I tuned (positioned or rotated) the TPS per the manual. This did not seem to improve anything. I need to recheck the resistance, voltage and continuity in the harness with the new TPS.
At this point you are probably thinking, this guy should send the car to the salvage yard. It obviously has so many things wrong with it, he will either spend a fortune on it or spend so much time troubleshooting, he will go nuts … and I would agree. The problem is, I am so intrigued by this problem, I would very much like to find out what is going on with this car! Now most of you have stopped reading at this point and found something more interesting to read. But, for those of you that are still reading, indulge me to describe some additional symptoms. For this I must digress.
Earlier in this post I mentioned that the car has had several ECMs. Before I received this car from my Dad, he replaced the original ECM with a refurbished unit. That, I heard, did not help the car’s performance for very long. I then inherited the car and I sent my son down to Alabama with a repaired ECM (I’ll call that ECM-1) to pick up the care and drive it back to Maryland. He dropped by the dealer and had the timing belt changed and had it checked out to make sure it was road worthy for the trip home. It drove perfectly on the way home and at home for about a month. Then it started to run rough. I’ll skip a couple ECMs and get to the ECM I bought from a salvage yard (call that ECM-2). I have both ECMs now and the following describes the car’s performance with each ECM after the repairs at the local dealer.
With ECM-1, the car smokes when it first starts, idles about right, intermittently runs rough and smooth at part throttle, dies when the throttle is pressed greater than half throttle, the speedometer does not work until it warms up; and the car will occasionally, but rarely, run perfect through the full range of acceleration. The codes remain 13 and 41 when it does not run perfectly.
With ECM-2, the car will not start for about ten seconds, will eventually start with the engine speed around 2K, no smoke, idle well, and have nearly no acceleration. I can get better acceleration by manually changing gears. Like the other ECM, I have experienced about four brief periods when the car ran perfectly and had no codes. This ECM now will not give DTC codes – it only shows the CEL on continually.
I am reluctant to buy another ECM or repair one I have until I find what is wrong. I will continue to troubleshoot and report any progress.
Continued to have codes 13 and 41.
Performed general engine troubleshooting:
Disconnected high-tension cord from right-side distributor. No spark from wire to ground. Found the insulation on the wire was burned through. Replaced all ignition wires.
Still no spark. Resistance of ignition coil primary and secondary OK. Voltage to coil and igniter OK. Harness OK. Replaced igniter.
Spark OK. Engine ran very rough.
Checked resistance of crankshaft position sensor and two cam shaft position sensors. Checked harness for opens and shorts.
Checked cam pulley position with crank at TDC. Lo and behold the right cam pulley was off two teeth. I called the dealer that installed the belt last summer (1K miles away) and the service manager there suggested I take the car to a local dealer and he would make it right if it was a workmanship problem. The local dealer found that it was not a workmanship problem. The insides of the right distributer had “exploded” and these parts created added friction, causing the belt to jump two teeth. The mechanic replaced the two distributer rotors and also replaced the right ignition coil, water thermostat and battery. Ouch.
The engine still ran poorly as I headed home from the dealer. I asked myself, what can I do now? Is it the ECM? Is it the wiring? I was still getting codes 13 & 41. It was time to troubleshoot the Throttle Position Sensor.
The TPS had the right resistance at the sensor and at the ECM. At idle and WOT, the voltage at the TPS and ECM did not fall within the specified range. I noticed a burn mark in the TPS connector and changed the connector and TPS. I tuned (positioned or rotated) the TPS per the manual. This did not seem to improve anything. I need to recheck the resistance, voltage and continuity in the harness with the new TPS.
At this point you are probably thinking, this guy should send the car to the salvage yard. It obviously has so many things wrong with it, he will either spend a fortune on it or spend so much time troubleshooting, he will go nuts … and I would agree. The problem is, I am so intrigued by this problem, I would very much like to find out what is going on with this car! Now most of you have stopped reading at this point and found something more interesting to read. But, for those of you that are still reading, indulge me to describe some additional symptoms. For this I must digress.
Earlier in this post I mentioned that the car has had several ECMs. Before I received this car from my Dad, he replaced the original ECM with a refurbished unit. That, I heard, did not help the car’s performance for very long. I then inherited the car and I sent my son down to Alabama with a repaired ECM (I’ll call that ECM-1) to pick up the care and drive it back to Maryland. He dropped by the dealer and had the timing belt changed and had it checked out to make sure it was road worthy for the trip home. It drove perfectly on the way home and at home for about a month. Then it started to run rough. I’ll skip a couple ECMs and get to the ECM I bought from a salvage yard (call that ECM-2). I have both ECMs now and the following describes the car’s performance with each ECM after the repairs at the local dealer.
With ECM-1, the car smokes when it first starts, idles about right, intermittently runs rough and smooth at part throttle, dies when the throttle is pressed greater than half throttle, the speedometer does not work until it warms up; and the car will occasionally, but rarely, run perfect through the full range of acceleration. The codes remain 13 and 41 when it does not run perfectly.
With ECM-2, the car will not start for about ten seconds, will eventually start with the engine speed around 2K, no smoke, idle well, and have nearly no acceleration. I can get better acceleration by manually changing gears. Like the other ECM, I have experienced about four brief periods when the car ran perfectly and had no codes. This ECM now will not give DTC codes – it only shows the CEL on continually.
I am reluctant to buy another ECM or repair one I have until I find what is wrong. I will continue to troubleshoot and report any progress.
07-05-12, 03:51 PM
#41
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After months of troubleshooting I think the Lexus is in pretty good shape now. I am very thankful for all the people that gave such insightful comments and helpful guidance.
Multiple mechanical and electrical failures made troubleshooting extremely difficult. This was complicated by my refusal to make partial repairs before I knew the full extent of all the repair needed.
Also, I learned that the ECM cannot accurately guide you through trouble shooting activities in all cases. Sometimes multiple problems confuse the ECM. Here are the last efforts that cleared the codes:
ECM-1 & ECM-2 are discussed above. I felt that I had eliminated all the electrical problems that were causing the ECMs to die, so I took a chance a bought an untested salvage yard (no returns) ECM, plugged it in and the car ran perfectly. It has run perfectly for a couple of months now.
One of the contributors to the electric problems was a short in the connector to the Throttle Position Sensor (TPS). Here's a picture. Notice the burn mark of the edge of the yellow face of the connector:
Multiple mechanical and electrical failures made troubleshooting extremely difficult. This was complicated by my refusal to make partial repairs before I knew the full extent of all the repair needed.
Also, I learned that the ECM cannot accurately guide you through trouble shooting activities in all cases. Sometimes multiple problems confuse the ECM. Here are the last efforts that cleared the codes:
ECM-1 & ECM-2 are discussed above. I felt that I had eliminated all the electrical problems that were causing the ECMs to die, so I took a chance a bought an untested salvage yard (no returns) ECM, plugged it in and the car ran perfectly. It has run perfectly for a couple of months now.
One of the contributors to the electric problems was a short in the connector to the Throttle Position Sensor (TPS). Here's a picture. Notice the burn mark of the edge of the yellow face of the connector:
07-05-12, 07:21 PM
#42
Moderator
Good for you, tbradford. Your efforts finally made it!
Congratulations on your big success.
Thank you for your write up. Your experience will sure help others.
Congratulations on your big success.
Thank you for your write up. Your experience will sure help others.
07-09-12, 11:48 AM
#43
Lexus Champion
I think I may have an ECM or TPS issue
sometimes my car goes into this crazy limp mode, A/C stops working, front defog light blinking, car stops shifting automatically (can be shifted manually though), check engine light comes on, and not running well - later, when the car is running perfectly again, there are no codes present!
ECM doesn't want to communicate with any scanner when in this limp mode
car is a 96 LS400
UPDATE!: SOLVED!!!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sometimes my car goes into this crazy limp mode, A/C stops working, front defog light blinking, car stops shifting automatically (can be shifted manually though), check engine light comes on, and not running well - later, when the car is running perfectly again, there are no codes present!
ECM doesn't want to communicate with any scanner when in this limp mode
car is a 96 LS400
UPDATE!: SOLVED!!!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Last edited by LScowboyLS; 11-26-12 at 10:20 PM.
11-23-12, 09:32 PM
#44
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I removed the tps and can't find any faults with the meter. I'll have to check voltages at the ecu to see if I can find trouble there.
11-26-12, 07:08 PM
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update... I replaced the 8 capacitors in the ecu and the car is back to normal. The power no longer cuts out when the pedal is pressed past a certain point.