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Old 05-09-2010, 10:02 PM   #1
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Default EBCM Troubles

We have been without ABS, traction control, and stability control for a few months now. The ABS, Low Trac, and BRAKE lights are constantly on. Sometimes if you start it and throw it into reverse or drive fast enough, the lights will be off, but within under a minute they come back on.

We recently have had the tire pressure read as "low" when it always used to read as -------- and this is what caused us to rethink the issue and take another look at things.

So far we have already checked:
-Fuses and Relays related to ABS
-Continuity in both grounds to the EBCM
-Constant and switched power to the EBCM
-The Data Link Communications from the PCM to the EBCM

No codes for anything like the yaw sensor, wheel speed sensors, steering wheel sensor, or any other ABS related sensor I've forgot. The only code we get is U1040(Loss of communications with the EBCM). Also, when we disconnect the EBCM completely we get about 3 new codes (simply because it'* just not hooked up) and the tire pressure reads ---------. After deleting the codes, re-connecting the EBCM and restarting the car, the only code we get is the U1040.

I spent a great deal of time looking through our dealer service manuals while Trent intelligently wired the wideband and we tried everything we could think of to fix it without being able to use a Tech 2 scan tool.

Is there anything we may have missed or need to try out?
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Old 05-09-2010, 10:11 PM   #2
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Check the ground on the engine block, rear of engine I think. If I remember right, that one is the sensor ground.
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Old 05-09-2010, 10:13 PM   #3
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Check the ground on the engine block, rear of engine I think. If I remember right, that one is the sensor ground.
I checked all the grounds for the engine and EBCM a week ago, and I also added a ground that I ran inside for the wideband so the added sensor was grounded to the same point to help eliminate voltage differences.
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Old 05-09-2010, 10:16 PM   #4
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Hmm, then I'm at a loss here. I'll have to put a little thought in to but right now I'm drawing a blank.
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Old 05-10-2010, 10:58 AM   #5
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I have one question.
What module is this code being pulled from ? I am going to assume PCM for the rest of this post
I will also assume you are not getting any other codes based on you post.
I looked up the trouble tree for this code in Alldata for U1040.
First step is to check batt and ign voltage to the effected mod. EBCM. (If there is a problem fix it and retest for code)
Next it says to test the grounds for the effected mod. ( If ok proceed)
Then it says to check for poor connection on the B+, Ground and Class 2 wires. ( If there is an issue fix them and retest)
If all the wiring to and from the EBCM is ok and working correctly then you probably need an ebcm :(
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Old 05-10-2010, 11:13 AM   #6
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Originally Posted by 2001SCBONNE View Post
I have one question.
What module is this code being pulled from ? I am going to assume PCM for the rest of this post
I will also assume you are not getting any other codes based on you post.
I looked up the trouble tree for this code in Alldata for U1040.
First step is to check batt and ign voltage to the effected mod. EBCM. (If there is a problem fix it and retest for code)
Next it says to test the grounds for the effected mod. ( If ok proceed)
Then it says to check for poor connection on the B+, Ground and Class 2 wires. ( If there is an issue fix them and retest)
If all the wiring to and from the EBCM is ok and working correctly then you probably need an ebcm :(
We only have an aeroforce scan gauge that we are pulling the codes from, so they are from the PCM, I am not sure if HPTuners can pull any more advanced diagnostics.
That sounds like the same trouble shooting step chart from the dealer service manual. and we have;
  • checked for constant and switched power (BATT and IGN3) at the plug for the EBCM
  • Checked the resistance of both the grounds for the EBCM, at the plug and gotten less then 2ohms of resistance (so very good grounds).
  • I checked for continuity in the wire going from the PCM to the EBCM and it is fine.
  • We have also replaced the EBCM with a tested good, used one.
  • I also checked the 5v sensor out from the EBCM to the Yaw Rate sensor in the trunk to make sure the EBCM was making the voltage change and the sensors were powered, and there was almost perfect 5v there.

The only thing I really haven't checked is the class 2 communication wire going away from the PCM, the one that goes through the entire car then back to the PCM. I really don't know where this wire even goes, the routing diagram shows it going from the EBCM and then splitting over up to three different paths.
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Old 05-10-2010, 11:42 AM   #7
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Quote:
Originally Posted by Rockstar04 View Post
The only thing I really haven't checked is the class 2 communication wire going away from the PCM, the one that goes through the entire car then back to the PCM. I really don't know where this wire even goes, the routing diagram shows it going from the EBCM and then splitting over up to three different paths.
Trent..with the Class 2 com system, a Tech II scanner will be needed. It sends the command to appropriate node, waits for the handshake then sends the command to on-off-reset or voltage. I don't know of any other way to test that part of the electrical.
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Old 05-10-2010, 11:47 AM   #8
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Trent..with the Class 2 com system, a Tech II scanner will be needed. It sends the command to appropriate node, waits for the handshake then sends the command to on-off-reset or voltage. I don't know of any other way to test that part of the electrical.
Well then I need to spend all today getting a job, so I can pay the retarded prices at the stealership for them to diagnose. . . . . . .

Actually it might be cheaper to buy my own Tech 2 for $1500. . .
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Old 05-10-2010, 11:50 AM   #9
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Originally Posted by Rockstar04 View Post
Well then I need to spend all today getting a job, so I can pay the retarded prices at the stealership for them to diagnose. . . . . . .

Actually it might be cheaper to buy my own Tech 2 for $1500. . .
The dealer up around here is pretty reasonable for a hook up and diagnose so you might check. It sure is cheaper than shelling out the $$ for a Tech II scanner.
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Old 05-10-2010, 02:29 PM   #10
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Well then I need to spend all today getting a job, so I can pay the retarded prices at the stealership for them to diagnose. . . . . . .
If you know someone that has a scanner that can get into the abs system you should be able to test the class 2 lines. If you can pull codes, read data, and run function tests etc in the EBCM I would think the class 2 lines work.
I do see you are at NIU. I live in Dupage Co. Do you come east out my way? If so I have a snap-on scanner I can hook up and have a look.
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