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Bad EATC killing my ECU?

Skaendo

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I have replaced my ECU twice already on my '97 Town Car, and I'm getting a couple of DTC's.

Both times the replacement ECU's went out just after 100 miles.


From the EATC self-test I get 125 and 115.

115 - intermittent engine coolant temp signal
125 - intermittent vehicle speed signal


From the ECU I am getting U1341 ,U1073 ,and P1000

U1341 - CAN data bus, A/C -vehicle speed invalid or missing data
U1073 - CAN data bus, cooling system -communication error
P1000 - System readiness test not complete


I have checked both the VCC and ECTS for voltage and ohms, both seem to check out fine. The wires and plugs look fine as well.

So, does the EATC store any DTC's (I wouldn't thunk so), could it be a bad EATC, or could it just be a cheap ECU service?

I have another ECU ready to put in from a ECU specialist, but I am being very cautious now after replacing it twice already.
 

bmarler

Member
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you're right to be cautious, after two failures it would seem that there's a wiring or sensor issue. intermittent problems are the worst. look at the wiring diagrams and look at all of the things that might be common to the problem. the pinpoint test procedures usually point you in the right direction so having a good manual set is important.
if you have the forscan software you can see live data and see if the signal is dropping out, or possibly monitor the voltage of the circuit. you can record the data and look at it later to try to figure it out.
i don't think the eatc stores any dtc's except the ones it gives you during the self test procedure.
 

Skaendo

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I have a Haynes manual, but they always say "These tests do not cover later models with OBDII". I did the checks anyways and they did come back normal with correct voltages and good resistance.

I am kind of leaning towards the EATC module, only because the A/C went out about a year ago and I just haven't bothered with it. I can't remember exactly when I started having issues, but I believe that it was just as winter was starting and I turned the heat on.

I am trying to rule out everything before replacing the EATC module. I did get some dirt/sand out of the VSS (Above typo VCC should have been VSS), so I'm going to go ahead and blow that out, replace the ECU and go through the drive cycle. (I have a lifetime warranty on the ECU now :) )

I do have FORScan and a Veepeak OBDCheck MS USB cable so I am going to have a friend ride with me during the drive cycle and monitor it.
 

Skaendo

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Well, I killed another ECU.

But I think that I am making progress. I pulled the DTCs and it gave me a:
B1352 - Ignition Key-In Circuit Failure

This does make some sense since the chime goes off almost constantly even when the key is not in the ignition. When I wiggle the ignition barrel the chime will go off.

So could a worn out ignition key barrel create a short and cause my ECU to fail?
______________________________
 
Last edited:

bmarler

Member
81
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Well, I killed another ECU.

But I think that I am making progress. I pulled the DTCs and it gave me a:
B1352 - Ignition Key-In Circuit Failure

This does make some sense since the chime goes off almost constantly even when the key is not in the ignition. When I wiggle the ignition barrel the chime will go off.

So could a worn out ignition key barrel create a short and cause my ECU to fail?
i would say yes. and since you can wiggle the ignition and make a change that's the most likely place to look for the short. time to pull apart the column and have a look.
 

Skaendo

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Well in an interesting turn of events I started a RMA on the ECU almost to finalizing it, one more email and it would have been on the way back to them.

In the meantime, I started digging into the B1352 DTC. I took the door apart and checked the switch and wire all the way back in through the frame, that all checked out good. Had the column apart and the key barrel out (the plastic piece where the key-in switch is loose, not sure if I want to replace the barrel now but probably will) and re-seated the key-in contact on the housing. Took the plug out of the ECU and visually inspected the pins, all fine.

Plugged the ECU back in, hooked the battery back up and gave it a crank. IT FIRED RIGHT UP.

The car no longer chimes all the time, only when the key is in and the door is open. I think that over time the key-in contact must have wiggled loose or around?

I also took the LCM out and blew it out with the compressor, but I don't think that that had anything to do with the all-of-a-sudden miracle of it working again.

Thanks for the help bmarler.
 

bmarler

Member
81
25
18
Well in an interesting turn of events I started a RMA on the ECU almost to finalizing it, one more email and it would have been on the way back to them.

In the meantime, I started digging into the B1352 DTC. I took the door apart and checked the switch and wire all the way back in through the frame, that all checked out good. Had the column apart and the key barrel out (the plastic piece where the key-in switch is loose, not sure if I want to replace the barrel now but probably will) and re-seated the key-in contact on the housing. Took the plug out of the ECU and visually inspected the pins, all fine.

Plugged the ECU back in, hooked the battery back up and gave it a crank. IT FIRED RIGHT UP.

The car no longer chimes all the time, only when the key is in and the door is open. I think that over time the key-in contact must have wiggled loose or around?

I also took the LCM out and blew it out with the compressor, but I don't think that that had anything to do with the all-of-a-sudden miracle of it working again.

Thanks for the help bmarler.
so glad you're up and running. those goofy electrical glitches are the worst. that key in contact must have been the culprit. whenever i take those connectors apart i use silicone grease on them (the contact pins) when i put them back together. that helps to protect them from further oxidation.
 

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