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Print in friendly format Send this term to a friend  4L80E
Automatic Transmission - 4 Speed

1st Gear: 2.43
2nd Gear: 1.49
3rd Gear: 1.00
4th Gear: 0.75

Reverse: 2.07

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bam 93 vett ABS/ASR code DTC72
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missouri
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The dash lights for the ABS/ASR are on all the time, I also do not hear the system self test after initial drive up to 6 mph. I am getting only DTC72, FSM says in the first step of diagnosis; "install off-board device" I assume this is some factory tester but don't know for sure, any ideas how I can start working on this? Thanks for any help.
Posted on: 2015/9/15 14:36
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bogus Re: 93 vett ABS/ASR code DTC72
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that is what they are suggesting...

ignore that comment and read past it. I am sure there is value there.
Posted on: 2015/9/15 20:52
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Matatk Re: 93 vett ABS/ASR code DTC72
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I haven't had a chance to check the FSM yet. The device they are referring to might be the tech 1. That was used in later years for diagnosis along with the ABS cartridge.
Posted on: 2015/9/16 10:38
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Woodstock Re: 93 vett ABS/ASR code DTC72
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Did the engine ever stall while having the code?
Posted on: 2015/9/16 13:23
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bam Re: 93 vett ABS/ASR code DTC72
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NO never stalled, have been replacing all the hard brake lines coming out of the ABS unit, two were leaking bad and all the rest (7 total) were badly rusted. Just got finished yesterday, it took a LONG time to totally bleed the brakes. Took it out for a drive and still have the code so hopefully I can start working on that now.
Posted on: 2015/9/28 14:53
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bogus Re: 93 vett ABS/ASR code DTC72
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I will have to dig, but there is a way to read codes from the EBCM via the speedometer.

Posted on: 2015/9/28 23:24
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Matatk Re: 93 vett ABS/ASR code DTC72
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Quote:

bogus wrote:
I will have to dig, but there is a way to read codes from the EBCM via the speedometer.



He already has the code, that's not the issue.

Display ABS/ASR DTCs
(Diagnostic Mode 9.1)

To display ABS/ASR DTCs, first select the EBTCM as the appropriate module by pressing the "TRIP RESET" until "9.0" is displayed in the trip monitor area of the cluster, then select the display DTCs mode by pressing the "TRIP/ODO" button until "9.1" appears. Then press the "ENG/MET" button to display the first DTC. Continue pressing the "ENG/MET" button to display additional ABS/AR DTCs until the End-Of-Information indicator ("---") is displayed in the speedometer. If it is necessary to go backward in the list, use the "FUEL INFO" button. The top of the DTC list will be indicated by the "---" display in the speedometer.
Posted on: 2015/10/1 0:11
Edited by Matatk on 2015/10/1 0:50:41
Edited by Matatk on 2015/10/1 0:50:56
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Matatk Re: 93 vett ABS/ASR code DTC72
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Quote:

bam wrote:
NO never stalled, have been replacing all the hard brake lines coming out of the ABS unit, two were leaking bad and all the rest (7 total) were badly rusted. Just got finished yesterday, it took a LONG time to totally bleed the brakes. Took it out for a drive and still have the code so hopefully I can start working on that now.


The code is unrelated to the brake lines.
Posted on: 2015/10/1 0:12
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Matatk Re: 93 vett ABS/ASR code DTC72
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Quote:

bam wrote:
The dash lights for the ABS/ASR are on all the time, I also do not hear the system self test after initial drive up to 6 mph. I am getting only DTC72, FSM says in the first step of diagnosis; "install off-board device" I assume this is some factory tester but don't know for sure, any ideas how I can start working on this? Thanks for any help.


Back to the beginning. From FSM 5E2-14:

The EBTCM can display the DTCs through the use of the Central Control Module (CCM) on-board diagnostic capabilities, the Tech 1 Diagnostic Computer, or the T-100 (CAMS) unit. In almost all instances in this section, diagnosis, information display, and system/component actuation will be described using the Tech 1. Refer to SECTION 8D for details on using the CCM diagnostics for the ABS/ASR system.

Based on that, there were two "off-board" systems for testing the EBTCM. The Tech 1, and the T-100. The T-100 was apparently a rare, full sized, roll around, computer based diagnostic machine used in GM dealers (based on what limited info I can find on the web). So when the troubleshooting guide says "off-board" device, this is why. Since the T-100 is obsolete and apparently extinct, you'll need a Tech 1.

As far as the code that you already retrieved, DTC72:

That is a serial data link malfunction, meaning there were errors in message transmission.

Using the Test Description section 5E2-108, Test 1 indicates that if you do not have an off-board device, you can use the CCM to attempt to communicate with the EBTCM. (see section 8D - display ABS/ASR DTCs).

So your first step in the troubleshooting tree is attempt to communicate with the EBTCM using the CCM. Since you already have the code, I will "assume" you got the code via the cluster? If that is the case, and you can communicate with the EBTCM, then you have no trouble there and you have to use the diagnostic aids under DTC 72.

The Diagnostic Aids state:

The problem may be intermittent. Try performing the tests shown while wiggling wiring and connectors; this can often cause the malfunction to appear.
CCM DTC 41 will likely be set along with this DTC if the problem is a short to ground or B+ on the serial data circuit.
If ABS/ASR DTC72 is set and CCM DTC 41 is not, the malfunction is likely to be an open between the EBTCM and the CCM.


So, that being said....

1) Do you have any other trouble codes (ie, CCM DTC 41)?
2) The other diagnostic tool needed is a J39700 breakout box, which allows you to test the voltage/resistance in the wires. This box looks pretty pricey for the average person.
3) If you don't have a CCM DTC 41, then you most likely have an open wire between the EBTCM and the CCM, and you'll need to track that down.
4) I would reset the code and see how quickly it comes back, or if you can make it appear by wiggling the connectors or individual wires.

Hope that helps.
Posted on: 2015/10/1 0:45
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bam Re: 93 vett ABS/ASR code DTC72
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Thanks for all the info Matatk. I do not have the DTC 41 only the 72. Tomorrow I will try the rest of the diagnosis w/o the tester that way I think I can find the bad wire, well see.
Posted on: 2015/10/3 3:23
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Matatk Re: 93 vett ABS/ASR code DTC72
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Sorry it took so long. Without the breakout box you might have trouble with the diagnosis. You might have to disconnect the ebtcm connector and the ccm connector and ohm the wires while wiggling them. I don't know the location of the connectors, so that is easier said than done, I'm sure.
Posted on: 2015/10/3 22:30
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