ECM Failure Symptoms

Stanley

Stanley

3rd Gear Poster
Joined
Oct 12, 2023
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196
Location
Canada
Vehicle Details
1997 Thunderbird 4.6L V8
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My engine randomly turns on and off a Check Engine Light lamp for days or weeks at a time, but checks have shown nothing and one mechanic thought that perhaps the ECM is failing. That one is rather random. More consistent is that, whenever I start the car, after about 10-15 seconds the "Low Coolant" lamp comes on, then shuts off after another short while, but the coolant levels are apparently fine. I'm wondering if these are signs of a failing ECM.

If so, are the Cardone remanufactured ECMs good to use, or is there another source people prefer?
 
Stanley said:
My engine randomly turns on and off a Check Engine Light lamp for days or weeks at a time, but checks have shown nothing and one mechanic thought that perhaps the ECM is failing. That one is rather random. More consistent is that, whenever I start the car, after about 10-15 seconds the "Low Coolant" lamp comes on, then shuts off after another short while, but the coolant levels are apparently fine. I'm wondering if these are signs of a failing ECM.

If so, are the Cardone remanufactured ECMs good to use, or is there another source people prefer?
Click to expand...

The low coolant light isn’t connected to the PCM, it’s a proprietary circuit as are most other lights and gauges, only the check engine light, overdrive light and tachometer are controlled by the PCM in these cars. That sounds like a fault with the level sensor in the tank.

As for the PCM that doesn’t sound like a typical symptom of them going bad(it’s actually very rare they outright fail, but they can develop faults). There’s usually accompanying stubborn codes associated to that though, what kind of code reader are you using? It’s possible it’s not recognizing the stored code when the light is on to display it
 
XR7-4.6 said:
As for the PCM that doesn’t sound like a typical symptom of them going bad(it’s actually very rare they outright fail, but they can develop faults). There’s usually accompanying stubborn codes associated to that though, what kind of code reader are you using? It’s possible it’s not recognizing the stored code when the light is on to display it
Click to expand...

I'm not using a reader myself, as I don't own one yet. I'm still very much in the "save me Mr. Mechanic" stage of car ownership. But this has been two different shops and has been going on for about two years now, so it's consistent in a few ways.

1997ThunderbirdLXV6 said:
When I first bought my car, I constantly had false positives from the low coolant light. Thoroughly cleaning the sensor terminals and washing out the tank put an end to that.
Click to expand...

That's good to know. Where are the sensor terminals, and is this something that you have to remove the tank for?
 
Stanley said:
That's good to know. Where are the sensor terminals, and is this something that you have to remove the tank for?
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On the V6, you just pull the sensor up and out of the tank; that doesn't require removing the tank. If you want to wash the tank, then yes, remove it.

I think on the V8, the tank is pressurized, so the design is different altogether.
 
If it makes you feel any better, the CEL on the '97 does the same thing, but it is because I have a broken elbow on a line going to the EVAP canister and I need to replace the purge valve and flow sensor. I'm not sure why a mechanic wouldn't be able to see any codes in the history though. Next time it is on go to an Autozone (or Canadian equivalent) and have them scan for codes to see what it is.
 
The ce light sounds like a bad o2 sensor. Have you ever replaced any? If not, get a new set nte is the oem. Do not buy bosch.
I usually move the fronts to the back, and the new ones in front. BUY a code reader; one that bluetooths to your phone is $20.
 
I suggest you invest in an inexpensive OBD2 code reader. Even the most basic one is easy to use and will let you find out what if any codes the car is setting. Everyone here is pretty helpful and can at least point you in the right direction, so you know what to expect at a shop.

As for the ECM going out yes it happens. It went out with no warning on my Cougar and I had to get the car towed home. It had a weird rev hang going on a few miles before it died, but otherwise was acting normal.

Also, I went with a Cardone Reman ECM from RA, and it had been trouble free. They have a few videos on their website that show they go through them well and do actually rebuild them for the most part.
 
Grog6 said:
The ce light sounds like a bad o2 sensor. Have you ever replaced any? If not, get a new set nte is the oem. Do not buy bosch.
I usually move the fronts to the back, and the new ones in front. BUY a code reader; one that bluetooths to your phone is $20.
Click to expand...

For the oxygen sensor brand, do you mean NTK? I see that at Rockauto, but no NTE. Also, do I want "downstream", or "upstream"?

And thanks all for the tips on the code reader: I'll get one.
 
Upstream & downstream are the same in our cars. Get 2 upstream and move your current upstream to the downstream, then toss the old downstream.
 
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