ECM year compatibility
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ECM year compatibility
I have a few issues that I believe are caused by the ECM in my 91.
First one is my CTS is not reading right. The sensor is reading correct however when hooked up to the harness it’s reading about 30° too high. I am getting 4440 ohm resistance between the yellow wire and ground. I could be wrong but I don’t think there should be any connection to ground on the yellow side because that would interfere with the reading from the sensor.
Now, I disconnected the harness from the ECM and testing the wires there’s no connection to ground. Using my meter and testing across pins C16 and ground (harness still disconnected), I get that same 4,440 ohm resistance.
second problem and this one is obvious, I was testing a bunch of things trying to isolate my long crank time when the engine is completely cold and I tapped on the ECM with the car running. It immediately shut off and fuel pressure dropped to 0 in about a second. Car started right back up and I could not duplicate the shut down again but it definitely happened. My luck and I’d be driving and hit a bump and have the car shut down...
My local scrap yard had an 85 corvette. Would I be able to grab the ECM from it and use my EEPROM in it? If not are any years compatible?
First one is my CTS is not reading right. The sensor is reading correct however when hooked up to the harness it’s reading about 30° too high. I am getting 4440 ohm resistance between the yellow wire and ground. I could be wrong but I don’t think there should be any connection to ground on the yellow side because that would interfere with the reading from the sensor.
Now, I disconnected the harness from the ECM and testing the wires there’s no connection to ground. Using my meter and testing across pins C16 and ground (harness still disconnected), I get that same 4,440 ohm resistance.
second problem and this one is obvious, I was testing a bunch of things trying to isolate my long crank time when the engine is completely cold and I tapped on the ECM with the car running. It immediately shut off and fuel pressure dropped to 0 in about a second. Car started right back up and I could not duplicate the shut down again but it definitely happened. My luck and I’d be driving and hit a bump and have the car shut down...
My local scrap yard had an 85 corvette. Would I be able to grab the ECM from it and use my EEPROM in it? If not are any years compatible?
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Thread Starter
Intermediate
Joined: Aug 2019
Posts: 42
Likes: 0
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 42
Likes: 0
At the ECM connector, ECM NOT connected, CTS NOT connected, resistance between C16 and C10 should be infinite.
At the ECM connector, ECM NOT connected, CTS NOT connected, resistance between C16 (yel/blk) and chassis ground should be infinite.
At the ECM connector, ECM NOT connected, CTS CONNECTED, the reading will be the resistance of the CTS sensor.
At the ECM connector, ECM NOT connected, CTS NOT connected, resistance between C16 (yel/blk) and chassis ground should be infinite.
At the ECM connector, ECM NOT connected, CTS CONNECTED, the reading will be the resistance of the CTS sensor.
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 42
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I don't know what you're asking, here.
You can't test "resistance" of the ECM at the ECM pins. With the wrong meter it is possible to damage solid state components. Never touch any meter to any pins on the ECM when it is disconnected. And you should only be checking ECM circuits if you know what you're doing with electrical diagnosis, or the results will be confusing and again, possibly damaging the ECM.
I don't think it is possible to write the "instructions" any clearer than I did. If all 3 checks I suggested returned the results I said they should be, there is no problem with your CTS wiring or circuit.
You can't test "resistance" of the ECM at the ECM pins. With the wrong meter it is possible to damage solid state components. Never touch any meter to any pins on the ECM when it is disconnected. And you should only be checking ECM circuits if you know what you're doing with electrical diagnosis, or the results will be confusing and again, possibly damaging the ECM.
I don't think it is possible to write the "instructions" any clearer than I did. If all 3 checks I suggested returned the results I said they should be, there is no problem with your CTS wiring or circuit.
Also the fact that I tapped on the ECM once and the car shut off immediately which has me wanting to swap it anyway. That is very unsafe in my opinion in the instance that I could hit a pot hole and have the car shut down.
The car has a very long cranking time. Like it’ll crank forever unless I crank a little, stop, and crank some more then it’ll go. Cold only and I for the life of me can’t figure it out. All the usual suspects have been addressed. Trying to think outside the box a little to figure this one out.
