94 Corolla - Multiple Engine Trouble Codes...?

[Tlander]

I have recently purchased a 94 Corolla DX 1.8L with 111,000k miles and a 4 speed AT; which is throwing multiple trouble codes, at seemingly random times. The previous owners had replaced the Timing belt, the Distributor, and the coolant Temp Sensor all to no avail. I have replaced the fuel filter(as it was the original) and have done a tune up as well with new wires, filters, plugs etc.

The codes which have been obtained were:

14 - Ignitor signal to ECU missing
22 - Water temperature sensor circuit fault
24 - Intake air temperature signal fault
52 - Knock Sensor fault

On one occassion the Overdrive Off light started flashing on and off as i was stopped at a light, it was as if i was pushing the button on and off in rapid succession. As i began to accelerate from the stop the light went out and never came on again, and the trans shifted into overdrive just fine.

When the check engine light isn't on, the car runs really good, aside from some abnormal vibration which appears to be a broken motor or trans mount. Otherwise it really runs well until the check engine light starts coming on, itermittently and whenever it does the engine hesitates, almost stalls etc etc. Then the light may go out for a few seconds or a few minutes and she runs great again.

I'm leaning towards a bad ECM or maybe a bad ground somewhere in the wiring harness? Does anyone know of any common trouble spots in the wiring, or of any known ECM problems with these cars? I've searched extensively on the web and haven't been able to find much info about cars which produce mutiple trouble codes like that, even when some of the sensors in question have already been replaced.

I'm thinking about grabbing a used ECM from a wrecked car in a junkyard to see if that solves this problem because i'd hate to buy a brand new one and then find out that it's a wiring problem after all.

Any help would be greatly appreciated!

[chinozie]

hi,

i) try to reset back the ECU...run the car for a few days...then see if any of those codes came out again or not...
ii) if nothing different...try to swap with another ECU...see how...

good luck...

[RIP]

If you haven't, check the connection at the ECU for security and corrosion. Disconnect the battery first but, make sure you have the activation code for the anti theft system.

[artmirza]

Originally Posted by Tlander

I have recently purchased a 94 Corolla DX 1.8L with 111,000k miles and a 4 speed AT; which is throwing multiple trouble codes, at seemingly random times. The previous owners had replaced the Timing belt, the Distributor, and the coolant Temp Sensor all to no avail. I have replaced the fuel filter(as it was the original) and have done a tune up as well with new wires, filters, plugs etc.

The codes which have been obtained were:

14 - Ignitor signal to ECU missing
22 - Water temperature sensor circuit fault
24 - Intake air temperature signal fault
52 - Knock Sensor fault

On one occassion the Overdrive Off light started flashing on and off as i was stopped at a light, it was as if i was pushing the button on and off in rapid succession. As i began to accelerate from the stop the light went out and never came on again, and the trans shifted into overdrive just fine.

When the check engine light isn't on, the car runs really good, aside from some abnormal vibration which appears to be a broken motor or trans mount. Otherwise it really runs well until the check engine light starts coming on, itermittently and whenever it does the engine hesitates, almost stalls etc etc. Then the light may go out for a few seconds or a few minutes and she runs great again.

I'm leaning towards a bad ECM or maybe a bad ground somewhere in the wiring harness? Does anyone know of any common trouble spots in the wiring, or of any known ECM problems with these cars? I've searched extensively on the web and haven't been able to find much info about cars which produce mutiple trouble codes like that, even when some of the sensors in question have already been replaced.

I'm thinking about grabbing a used ECM from a wrecked car in a junkyard to see if that solves this problem because i'd hate to buy a brand new one and then find out that it's a wiring problem after all.

Any help would be greatly appreciated!

can u please tell what was solution i am having same problem

[artmirza]

can someone please post a solution that worked for this problem i am having exact same problem

[Tlander]

Well, for whoever comes across this having similar problems, hopefully you are having the same issue that I was. I say hopefully, because after messing around with it and cussing it out for a few months I finally discovered that the source of ALL of those FALSE check engine codes was a single, loose ground wire!

There is evidentally a very crucial ground that comes right off of the main wire harness. What you do is find the main harness as it passes through the firewall into the engine compartment, I got to it easier from the passenger side fender. When you find the main harness, follow it till it comes near the engine block, there is a single wire that goes from there and is bolted directly to either the block or the head on the back side of the engine(closest to the firewall). This sucker is pretty hidden so it may take some work finding it.

On my car what happened was a)it was covered with years of sludge due to a valve cover gasket leak that wasn't fixed by the previous owner, and b)the 8 or 10mm bolt which holds the wire in was actually loose, which by itself could cause an intermittent ground short and apparently- a whole world of troubles for the computer. Oh, and I did replace the ECM first, but of course that fixed nothing.

Good luck! That little bolt is not easy to get to once you do find it.

[artmirza]

thank you for posting a reply so fast. I am having exact same problem to the TE. Same codes keep popping. same driving issues. same repairs made. I was going to change ecu next. But thank GOD I found your post. Come to think of it I first Noticed this problem although it was not so severe about a year ago when I had my starter replaced which is in the same area where you describe the loose wire was.

I am going to look for that wire. please if you can provide any additional info perhaps more accurately pinpoint its location anything ....

thank you most grateful. GOD BLESS

[Tlander]

I can't remember too many details since it's been three years, but I think I used a flashlight to spot the ground wire. The problem is that it'll probably be coated with black grease, making it harder to spot of course.
Oh, I did use some spray degreaser like Engine Bright, etc, just be careful not to get too much onto any electrical connectors, etc. As far as I can recall, that wire bolts into the block or the head a little towards the passenger side from the back-center of the engine, if that makes any sense. It's below the intake manifold, and behind the water pump if you are looking at the engine from the right front fender.

[artmirza]

The wire harness breaks off into several different directions shortly after coming out of firewall, A single wire that comes of this main junction goes to the tranny.. Other wires break off and go to TPS , engine coolant temp. sensor, distributor etc.. One goes to diagnostic connector.. The main harness carries on straight to battery and fuse boxes. There is only one other set of thick wire bundle that breaks of this main junction and goes right behind the engine and breaks off again, almost immediately, going to starter, fuel injectors and carries on to the A/C compressor, alternator and a few other visible sensors.

From this second junction where the fuel injector and starter wires break off, is either a single or dual wire ( covered in insulation so hard to tell ) that seems to be bolted to engine. It is right above the starter. It is difficult to see and I was only able to trace it with my fingers and felt it was bolted to engine with a single bolt.

Is this the wire that you are talking about? Of course it was grimy but seemed pretty tightly bolted. Is this not the knock sensor wire cos it was hard to tell. I don't know if knock sensor has plastic connector. This did not seem to have a plastic connector at the end.

Sorry for the bother but any additional help would be appreciated from anyone. Thank you.

[Tlander]

I think that's the same wire that fixed the problem for me. It was a little loose, but extremely grimy so I unbolted it, sprayed it down heavily w/ de-greaser, then tightened it back down snug. It was not an easy task, took me a couple of hours due to such tight clearances, I think I got to that bolt using a box ended wrench. If you have one of those ratcheting types it'll make life a whole lot easier.

If that doesn't solve the problem, then maybe it could be a bad ground closer to the ECU? Or, the computer could be fried after all.