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So my mom's LS400 1992 recently stopped running. It cranks over but doesn't start. I entered it into diagnostic mode and got at engine code 12.
So I took out the passenger side Camshaft sensor and found that it had been spliced before and was badly done using a crimp tool. I redid it by soldering then tested it and it seemed to be doing fine. I reinstalled the camshaft sensor and the error code went away but the car still cranked but wouldn't start. I then read about a lot of people having ECU issues because of the capacitors leaking. I ended up replacing the capacitors on the ECU and reinstalled it into the car. Again it would crank but not start. The check engine light was on again, giving a 12 code. So I took out both camshaft sensors and the crankshaft sensor. I checked their ohms rating and all were around 1100 ohms. Then I also tested if I would get a voltage coming out of it if I moved it near metal and away from metal and that created voltage. I am assuming they are still good but not 100% sure without a oscilloscope though even with one I wouldn't know how to test it. I am now believing it is a wiring issue so I checked continuity on all the wires the ground came out fine. I used a wire to check for continuity on the other wire for each sensor. Both camshaft sensors had continuity to the ECU pins. But then I found out that the Crankshaft sensor had continuity to Two pins going into the ECU. I've been trying to get my hands on a 1992 wiring diagram to see where there could be a short... or if it should be like this. Here are some pictures of the pins used by my Lexus.
I don't remember what camshaft sensor went to which pin but they each were separate. While the crankshaft had 2 pins.
I put the car back together to gave it a shot, and nothing does anyone have the pinouts for the ecu so I can see what pins this should be.
Also if anyone needs clarification on anything just ask. thank you.
Im not too familiar with the UCF10 CEL codes, but since the codes you're getting pertain to the crankshaft/camshaft, have you checked to see if the timing is still good? Perhaps the car skipped timing? Just a shot in the dim, not quite dark. Also, crankshaft and camshaft position sensors are very cheap and easy to replace. The crank sensor on my 98 had a resistance of 2100ohms, which the internet said was too high. So i bought a new OEM Denso sensor, and out of the box it also read 2100ohms. Installed it anyway and the car has ran great ever since. The symptom I had was random stalling out with no CEL. I think maybe just the connector to the sensor needed cleaning out, it was gunky and grimy, or the sensor had a weird internal failure that revealed itself with heat.
I have not checked timing, the timing belt was replace about a year ago it was correct then I dont have a reason to suspect it went bad already but Ill check it just to make sure. I have not replace any sensor because I dont believe it is the sensor I believe I have an electrical short with the crank shaft sensor. Since the yellow on the crankshaft sensor is now connected with two pins on the ECU plug. While the white wire is connected to ground.
The code 12 means not only cam position sensors but also the crank position sensor. In those days when the OBD-II was not introduced yet, Toyota set up the code systemToyotacomputer controlled system so called TCCS and the algorithm of it is simpler and the code 12 does not separate those sensors. You need to check the crank position sensor too when you get the code 12.
The code 12 means not only cam position sensors but also the crank position sensor. In those days when the OBD-II was not introduced yet, Toyota set up the code systemToyotacomputer controlled system so called TCCS and the algorithm of it is simpler and the code 12 does not separate those sensors. You need to check the crank position sensor too when you get the code 12.
so what are you suggesting to change ? I have 3 ecus and they all do the same I've changed my crank sensor 3 times three different ones all working
so what are you suggesting to change ? I have 3 ecus and they all do the same I've changed my crank sensor 3 times three different ones all working
The best way to troubleshoot is to observe waveforms using an oscilloscope. Those 3 signals are phased like this below and the amplitude is about 5 to 6Vp-p each. This chart refers the idling rpm. The frequency goes higher as the rpm rises. Cam signals should appear every time 24 pulses are generated by the crank position sensor and the bank 2 cam signal comes up 12 pulses after the bank 1 cam signal. Without an oscilloscope, you can't check this.
Modern cars need to use electronics tools such as a multimeter and an oscilloscope to troubleshoot. Oscilloscopes are not expensive any more these days. You can buy it just paying less money compared with an hour charge of most mechanics. I have an old very expensive one and an inexpensive latest one which only costed 70 US dollars. https://www.ebay.com/b/Digital-Oscil...?rt=nc&_sop=15
07-30-19, 09:44 PM
LS400 92 code 12 wiring issue
