Roof fails during movement (DTC Code B2536); Solution including truck latch removal
05-30-12, 08:12 AM
#20
Racer
Thread Starter
I've been waiting to make sure the fix is really the fix, but things seem pretty solid. I'm going to give the long-winded version because: (1) I think we did a better job than the Lexus techs would have done and (2) my wife just isn't interested in this stuff! Also, a shout-out to VVTiBob (aka the Guru) because without his input, we would not have had a clue.
We went to the Lexus dealership on Sunday and got them to do a scan after a "bad" top sequence (i.e. fail). Received a DTC code of B2536. Thank you, Lexus dealer, and Buh-Bye.
The B2536 code points to the "Luggage Courtesy Switch Malfunction." Translated to English, this is the switch that tells the roof computer (ECU) whether the trunk is closed.
Got the B2536 diagnostic procedure worksheet from VVTiBob. The procedure is:
1. Connections may be bad
2. Switch may be bad
3. ECU may be bad.
Connections were fine, so we zeroed in on the switch next. The switch tested fine in the open position and tested fine in the closed position, per the Lexus testing protocol. At this point there is no doubt in my mind that the Lexus tech would have ordered a new ECU. After all, that is exactly the next step in the diagnostic flow chart once the switch tests good.
But Habious came up with the bright idea that the failure occurred just after the top started to move, i.e. while the unit was in motion. Meaning the ECU was being told initially that things were AOK and to start the operation. Only then did it fail. We decided to bypass the switch entirely and see whether that would make a difference.
So we disconnected the switch and simulated a "trunk closed" condition by shorting two of the switch pins (thanks again for the pin-out diagram, VVTiBob).
But now, the top didn't work at all. In fact, the red light on the dash switch didn't even come on. Again props to Habious who figured out what was going on.
We had the trunk open to get at the switch and simulate the "trunk closed" condition. So the ECU was getting two conflicting messages at the same time: "trunk open" AND "trunk closed" because it is a single pole, double throw switch (SPDT). With that conflict, it wasn't about to start.
But how could we remove the switch and short the connectors WHILE the trunk is down??? Neither Habious nor I are small enough to crawl inside the trunk with the lid closed!!
We came up with the idea of disconnecting the switch and shorting the pins with the trunk open, as we did before. But then close the trunk and pull the battery. When reconnected, the ECU sees only the trunk down condition and we have removed the switch from the circuit.
This worked and seems to have solved the problem, thereby identifying the switch as the culprit. The switch is good in the trunk down/up position but fails during movement. The contact probably rides an arc during the movement and hits a bad spot, causing the failure.
"Good at Rest, Faulty During Movement" is not in the Lexus diagnosis manual, so I'm sure Lexus would have replaced the roof ECU (the next step) and charged me $1,750 for that part.
I have the switch on order for the permanent fix (forever bypassing the trunk closed switch is not a good idea). Thanks to everyone who helped!
We went to the Lexus dealership on Sunday and got them to do a scan after a "bad" top sequence (i.e. fail). Received a DTC code of B2536. Thank you, Lexus dealer, and Buh-Bye.
The B2536 code points to the "Luggage Courtesy Switch Malfunction." Translated to English, this is the switch that tells the roof computer (ECU) whether the trunk is closed.
Got the B2536 diagnostic procedure worksheet from VVTiBob. The procedure is:
1. Connections may be bad
2. Switch may be bad
3. ECU may be bad.
Connections were fine, so we zeroed in on the switch next. The switch tested fine in the open position and tested fine in the closed position, per the Lexus testing protocol. At this point there is no doubt in my mind that the Lexus tech would have ordered a new ECU. After all, that is exactly the next step in the diagnostic flow chart once the switch tests good.
But Habious came up with the bright idea that the failure occurred just after the top started to move, i.e. while the unit was in motion. Meaning the ECU was being told initially that things were AOK and to start the operation. Only then did it fail. We decided to bypass the switch entirely and see whether that would make a difference.
So we disconnected the switch and simulated a "trunk closed" condition by shorting two of the switch pins (thanks again for the pin-out diagram, VVTiBob).
But now, the top didn't work at all. In fact, the red light on the dash switch didn't even come on. Again props to Habious who figured out what was going on.
We had the trunk open to get at the switch and simulate the "trunk closed" condition. So the ECU was getting two conflicting messages at the same time: "trunk open" AND "trunk closed" because it is a single pole, double throw switch (SPDT). With that conflict, it wasn't about to start.
But how could we remove the switch and short the connectors WHILE the trunk is down??? Neither Habious nor I are small enough to crawl inside the trunk with the lid closed!!
We came up with the idea of disconnecting the switch and shorting the pins with the trunk open, as we did before. But then close the trunk and pull the battery. When reconnected, the ECU sees only the trunk down condition and we have removed the switch from the circuit.
This worked and seems to have solved the problem, thereby identifying the switch as the culprit. The switch is good in the trunk down/up position but fails during movement. The contact probably rides an arc during the movement and hits a bad spot, causing the failure.
"Good at Rest, Faulty During Movement" is not in the Lexus diagnosis manual, so I'm sure Lexus would have replaced the roof ECU (the next step) and charged me $1,750 for that part.
I have the switch on order for the permanent fix (forever bypassing the trunk closed switch is not a good idea). Thanks to everyone who helped!
Last edited by JohnnyCake; 05-30-12 at 08:21 AM.
05-30-12, 08:37 AM
#21
The dynamic duo rules again
I've been waiting to make sure the fix is really the fix, but things seem pretty solid. I'm going to give the long-winded version because: (1) I think we did a better job than the Lexus techs would have done and (2) my wife just isn't interested in this stuff! Also, a shout-out to VVTiBob (aka the Guru) because without his input, we would not have had a clue.
We went to the Lexus dealership on Sunday and got them to do a scan after a "bad" top sequence (i.e. fail). Received a DTC code of B2536. Thank you, Lexus dealer, and Buh-Bye.
The B2536 code points to the "Luggage Courtesy Switch Malfunction." Translated to English, this is the switch that tells the roof computer (ECU) whether the trunk is closed.
Got the B2536 diagnostic procedure worksheet from VVTiBob. The procedure is:
1. Connections may be bad
2. Switch may be bad
3. ECU may be bad.
Connections were fine, so we zeroed in on the switch next. The switch tested fine in the open position and tested fine in the closed position, per the Lexus testing protocol. At this point there is no doubt in my mind that the Lexus tech would have ordered a new ECU. After all, that is exactly the next step in the diagnostic flow chart once the switch tests good.
But Habious came up with the bright idea that the failure occurred just after the top started to move, i.e. while the unit was in motion. Meaning the ECU was being told initially that things were AOK and to start the operation. Only then did it fail. We decided to bypass the switch entirely and see whether that would make a difference.
So we disconnected the switch and simulated a "trunk closed" condition by shorting two of the switch pins (thanks again for the pin-out diagram, VVTiBob).
But now, the top didn't work at all. In fact, the red light on the dash switch didn't even come on. Again props to Habious who figured out what was going on.
We had the trunk open to get at the switch and simulate the "trunk closed" condition. So the ECU was getting two conflicting messages at the same time: "trunk open" AND "trunk closed" because it is a single pole, double throw switch (SPDT). With that conflict, it wasn't about to start.
But how could we remove the switch and short the connectors WHILE the trunk is down??? Neither Habious nor I are small enough to crawl inside the trunk with the lid closed!!
We came up with the idea of disconnecting the switch and shorting the pins with the trunk open, as we did before. But then close the trunk and pull the battery. When reconnected, the ECU sees only the trunk down condition and we have removed the switch from the circuit.
This worked and seems to have solved the problem, thereby identifying the switch as the culprit. The switch is good in the trunk down/up position but fails during movement. The contact probably rides an arc during the movement and hits a bad spot, causing the failure.
"Good at Rest, Faulty During Movement" is not in the Lexus diagnosis manual, so I'm sure Lexus would have replaced the roof ECU (the next step) and charged me $1,750 for that part.
I have the switch on order for the permanent fix (forever bypassing the trunk closed switch is not a good idea). Thanks to everyone who helped!
We went to the Lexus dealership on Sunday and got them to do a scan after a "bad" top sequence (i.e. fail). Received a DTC code of B2536. Thank you, Lexus dealer, and Buh-Bye.
The B2536 code points to the "Luggage Courtesy Switch Malfunction." Translated to English, this is the switch that tells the roof computer (ECU) whether the trunk is closed.
Got the B2536 diagnostic procedure worksheet from VVTiBob. The procedure is:
1. Connections may be bad
2. Switch may be bad
3. ECU may be bad.
Connections were fine, so we zeroed in on the switch next. The switch tested fine in the open position and tested fine in the closed position, per the Lexus testing protocol. At this point there is no doubt in my mind that the Lexus tech would have ordered a new ECU. After all, that is exactly the next step in the diagnostic flow chart once the switch tests good.
But Habious came up with the bright idea that the failure occurred just after the top started to move, i.e. while the unit was in motion. Meaning the ECU was being told initially that things were AOK and to start the operation. Only then did it fail. We decided to bypass the switch entirely and see whether that would make a difference.
So we disconnected the switch and simulated a "trunk closed" condition by shorting two of the switch pins (thanks again for the pin-out diagram, VVTiBob).
But now, the top didn't work at all. In fact, the red light on the dash switch didn't even come on. Again props to Habious who figured out what was going on.
We had the trunk open to get at the switch and simulate the "trunk closed" condition. So the ECU was getting two conflicting messages at the same time: "trunk open" AND "trunk closed" because it is a single pole, double throw switch (SPDT). With that conflict, it wasn't about to start.
But how could we remove the switch and short the connectors WHILE the trunk is down??? Neither Habious nor I are small enough to crawl inside the trunk with the lid closed!!
We came up with the idea of disconnecting the switch and shorting the pins with the trunk open, as we did before. But then close the trunk and pull the battery. When reconnected, the ECU sees only the trunk down condition and we have removed the switch from the circuit.
This worked and seems to have solved the problem, thereby identifying the switch as the culprit. The switch is good in the trunk down/up position but fails during movement. The contact probably rides an arc during the movement and hits a bad spot, causing the failure.
"Good at Rest, Faulty During Movement" is not in the Lexus diagnosis manual, so I'm sure Lexus would have replaced the roof ECU (the next step) and charged me $1,750 for that part.
I have the switch on order for the permanent fix (forever bypassing the trunk closed switch is not a good idea). Thanks to everyone who helped!
So how much was the switch ? Once you pull it out you might be able to test the old switch to see where during the movment it failed . I wonder if there was any way adjusting the tension of the switch / during its arc.
05-30-12, 11:01 AM
#23
This was sure a fun problem to track down.
Of course, JohnnyCake (JC) never comes to me with the easy ones.
It was failing 3 out of 4 times but, with the "switch bypass" in place, it was 100% (there was one point where it failed...and we were both like "Oh crap, I guess we DIDN'T fix it!"...but it turns out the temporary jumper was a bit too temporary, and had slipped out of the harness).
JC has had it "fixed" for a couple of days now and, I'm assuming (since my cell phone isn't ringing off the hook) that it's still working like a champ.
The little switch bypass trick did two things for us...
A) Verified without-a-doubt that the truck lid switch is the root cause of his top failure
B) Provided JC with a temporary fix...his convertible is yet again a convertible.
The only reason we can't just leave it this way is...he can't open the truck without confusing the heck out of the Roof ECU. If JC opens the trunk, the Roof ECU gets the "The trunk is open AND the truck is closed" messages and locks out the top. Only way to get the top working after opening the trunk (in this bypassed configuration) is to close the trunk and pull the battery cable, resetting the Roof ECU.
I'm not sure yet if we're replacing the switch or having the local dealer replace it. Looks like a bit of a PITA to get to. If the dealership only wants a couple hundred bucks in labor (with our supplied part), I think it's worth it to have them skin their knuckles.
Of course, I'm a bit biased...it's NOT my couple-hundred bucks and it IS my knuckles!
Of course, JohnnyCake (JC) never comes to me with the easy ones.
It was failing 3 out of 4 times but, with the "switch bypass" in place, it was 100% (there was one point where it failed...and we were both like "Oh crap, I guess we DIDN'T fix it!"...but it turns out the temporary jumper was a bit too temporary, and had slipped out of the harness).
JC has had it "fixed" for a couple of days now and, I'm assuming (since my cell phone isn't ringing off the hook) that it's still working like a champ.
The little switch bypass trick did two things for us...
A) Verified without-a-doubt that the truck lid switch is the root cause of his top failure
B) Provided JC with a temporary fix...his convertible is yet again a convertible.
The only reason we can't just leave it this way is...he can't open the truck without confusing the heck out of the Roof ECU. If JC opens the trunk, the Roof ECU gets the "The trunk is open AND the truck is closed" messages and locks out the top. Only way to get the top working after opening the trunk (in this bypassed configuration) is to close the trunk and pull the battery cable, resetting the Roof ECU.
I'm not sure yet if we're replacing the switch or having the local dealer replace it. Looks like a bit of a PITA to get to. If the dealership only wants a couple hundred bucks in labor (with our supplied part), I think it's worth it to have them skin their knuckles.
Of course, I'm a bit biased...it's NOT my couple-hundred bucks and it IS my knuckles!
05-30-12, 11:14 AM
#24
Moderator
05-30-12, 11:26 AM
#25
Moderator
So where are we going for steak dinners? If nothing else, I can be there in the spirt of DIY'ers. The switch should run around $100. DIY labor, priceless.
Johnny if you do the switch replacement yourself, I too would like to see a nice DIY write up...pictures would be nice too.
Johnny if you do the switch replacement yourself, I too would like to see a nice DIY write up...pictures would be nice too.
05-30-12, 07:24 PM
#28
Moderator
