grumpy55

Hi to everyone,
I am new here as you can probably tell.
I have a question regarding fault codes on a 1994? LS400.
The check engine light came on the other day so I proceeded to troubleshoot the fault codes.
The following codes are showing up repeatedly even after clearing them.
13: Possible crank position or/and cam position sensor.
21: Main oxygen sensor left.
24: IAT sensor.
28: Main oxygen sensor right.
31: Air flow meter.
How is it possible for this engine to start and run with so many faulty sensors.
Or am I missing something bigger that could be causing such a major malfunction.
Any help or guidance on where to start looking is muchly appreciated.
Cheers.

Banshee365

https://www.clublexus.com/forums/ls-...capacitor.html

dicer

X2, we agree again Banshee.

Banshee365

On a roll!

grumpy55

Hi guys,
Sorry for the late reply but I get one day a week to work on this project.
I was hoping for more discussion on this but you seem set on the ECU.
I pulled the ECU and opened it up. Looks brand new inside. No leaks. No rust or corrosion anywhere. Not even a slight bulge in any capacitor.
I sure hope you are right on this.
Where I live I have no facilities for testing. No one is interested in the soldering job if I buy the capacitors.
My only option is to shop it out to Injectronics for an evaluation at $175.00 or repair for $750.00. But no fix no pay. Just the $175.00 for telling me it's no good.
By the way the ECU is out of a 1992 LS400 not a 1994 as first stated. Part number # 89661-50070.
I believe it is out of a RHD Australian or jap import vehicle.

Banshee365

You can ripple test the ECM. Just because the capacitors agents leaking yet doesn't mean they aren't bad. I'm not saying this is 100% your problem but it sure sounds like it. Those malfunctions should not cause the car to not run. I'm not totally sure on the LS400 but many cars can infer engine speed from cam signals of the CKP circuit fails for some reason. Same goes if CMP fails.

deanshark

Just throwing my experience out. Although the ECU is known for bad caps I would do some checking on the sensors before spending money on something that might not be bad. On my 93 I had all these codes come up close to the same time. My AFM was bad (24 and 31) which put the ECU in safe mode so it would run right. But with that there was so much raw fuel going through so it gave me the codes for the O2 sensors. (21 and 28) The only time I had a code 13 is when my timing belt jumped a tooth. But that could be the crank or cams sensors, or the wiring to them. Sometimes the wires hang loose and get cut by the serpentine belt.

I'm not disagreeing with dicer and Banshee, (I wouldn't want to do that ) Just saying what happened with mine.
You never mentioned how the car runs with these codes, like acceleration problems, hesitations, or a minor or major skip?
How many miles on the car?

Banshee365

I would have to say that is certainly plausible. Without OBD2 diagnosis is a bit more difficult without reading raw data from the sensors in a waveform and knowing exactly what they should say. Check the wiring to the AFM as well. Sometimes when several codes come up out of no where a rodent had a snack on some wiring. Something to think about.

deanshark

I thought that only happened to me.

grumpy55

Now we have some food for thought here. I'm not denying the ecu is the culprit but if I can try some other avenues before outlaying the big bucks that would make me and my wallet feel a bit better. The Rodent suggestion is a possibility as the vehicle was parked up for several months in a shed before I resumed work on it. The check engine light has never appeared before not blinking or solid while car is running. It appeared after replacing the serpentine belt and both idler pulleys for some reason. The car starts and idles fine "sometimes". Other times it starts and idles rough. I can increase the revs to about 3,000 rpm and the engine will start to break down or misfire. The check engine light blinks in time to the misfire. The smell of un-burnt fuel (running rich) has been obvious since I first bought the vehicle. I will have a good look around the wiring to see if anything has been chewed or rubbed through on a belt maybe. And many thanks for the help and suggestions so far.
Ran a resistance test on AFM with a reading of 5ohms and a very faint continuity light. Does that mean anything.

djamps

To quickly rule out/in the ECU, do the ripple test as outlined in the ECU mega thread. Also, if you've ran rich for a while you likely have permanently damaged the catalyst and/or o2 sensors. I'd put my money on the ECU and possibility of collateral damage.

grumpy55

Thanks for the suggestion of ripple test. But my OBD1 does not have an OP1 socket. The only mention of OP is an OPT socket. Any other suggestions.

djamps

If my memory serves correct,I believe you can measure the ripple on the MAF sensor's power line which is regulated by the ECM.

grumpy55

Ok then. Do I still need the capacitor in place. And which wire is the power wire. Thank you.

djamps

Can't help ya there, never done the test myself. Sort thru the whole thread, it's all in there.