# ABS lost communication issue



## Azztheboy (Apr 17, 2020)

*I need a wiring diagram pinouts for 2012 CRUZE ABS plug at the module/pump connector.*

A few days ago, in the midst of the ongoing stupid "service power steering" "Traction control" warnings...The ABS light came up. (I replaced the battery terminal on the earth cable to try to solve those low voltage/ resistance issues that all these early cruzes suffer from - but those warnings persist).
I now also have the ABS light now.
So now when I scan the car on enhanced Chevy OEM - get U0121-00 ECM Lost communication with the Electronic Brake Control Module. and U0121-00 TCM -Trans Control Module - Lost communication with Electronic brake control module.

So I try connect directly to the ABS module - using the ABS feature of this scan tool - NEGATIVE! Can't see it - communication error - (no surprise)

So checked the two fuses in the fuse box. The bigger J FUSE 30AMP and the micro 15amp. All good.

*SO: I purchased a brand new genuine OEM chevy ABS pump listed for 2011-2015. ($100)*

So I unplugged the old ABS - and put the plug into the new unit (before I undo all hydraulics) - then got the car into "on mode" (engine not on) and reconnect scan tool - and still, it can't see that new pump either.

So - I wonder if this pump has to be coded. or why CAN bus isnt making a connection...

So - I need pin outs for that dirty big plug. I know that the CAN bus wiring is in those wires - I want to look back at the ECU and see about 60 ohms across that bus (if the ECU is visible and not at fault). I also want to see that its getting 12v and earth's are all good...

Id love all this to be a bad earth ! Save me $100 bucks....

Anyone have a wiring diagram for ABS - particularly the pinouts for the ABS pump/module Assembly.
Thanks in advance Team


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## Snipesy (Dec 7, 2015)

If the scan tool calls it ABS and not the full proper name, Electronic Brake Control Module, then it probably won’t work with that scan tool. More than likely the module is working fine.
Did you replace the negative battery cable get?


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## Azztheboy (Apr 17, 2020)

Hi Snipesy,
last month when I got this car and scanned it, I could connect to the ABS with my scan tool. I think it reported some minor code at the time (maybe low voltage - I can't remember). So my scan tool has that capacity - and the module was happy to connect. NOT NOW for some obscure reason. 

My scan tool isn't the 700$ version - its a 179$ version from HF.

Any way... I have access to a 750$ tool which I might borrow and see what I get.

Still looking for pin outs so I can check power supply / earths and CAN bus high and low.

I'm going to change out those the two troublesome earth cables and the positive one from the alternator. The PCV valve guy sells the set for 45$

Thanks
Aaron


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## plano-doug (Jul 1, 2015)

Azztheboy said:


> Still looking for pin outs so I can check power supply / earths and CAN bus high and low.


Below is what I culled for the EBCM pinout.

Also attached is an annotated drawing showing the Data Link Controller (OBD2 port) connector pinout for a 2013 Cruze. I think the 2012 should be the same. Perhaps this will help, too.

Doug



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## Azztheboy (Apr 17, 2020)

Thanks Plano- Doug.
I'll take a look at what's going on in the plug.
The pin outs are helpful too - because I can test every wheel ABS sensor from that plug pin out.

Any way found this: 2020 diagnosis for NO Communication result of your scanner using diagnostic link connector

It makes some sense of how the DLC connector pin outs work and how the GMLAN works.

I will post back what I find.
Aaron


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## Azztheboy (Apr 17, 2020)

So I tested the pins in the ABS module connector for Power supply and ground. (all good) 
I tested the GMLAN Bus (checked the resistance across the High-speed GMLAN serial data pos and neg across pins 9&11 and across 5&6.)
I get 120 Ohms (instead of 60).
This is looking back up the bus to ECU.
I have to find which module is bad that is screwing things up. They are all daisy-chained I think in series.
I have a pro electrical guy coaching me. I'll come back when I get to the bottom of this.
Aaron


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## plano-doug (Jul 1, 2015)

Azztheboy said:


> I tested the GMLAN Bus (checked the resistance across the High-speed GMLAN serial data pos and neg across pins 9&11 and across 5&6.)
> I get 120 Ohms (instead of 60).


I think I can explain that. At each end of the line, there is a 120 ohm resistor. Together (ie, in parallel) they form 60 ohms of resistance. With the cables disconnected from the EBCM, the 120 ohm resistors on that end are removed, leaving only the resistors at the other end in the circuit.

Also, I think you should see 120 ohms between pins 10-12.

I have attached some more drawings which may be helpful. These are what I've been studying, trying to get up to speed on this stuff.

HTH.
Doug

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## Azztheboy (Apr 17, 2020)

Hi Doug, (and every one else ). I wanted
To report back what happened. So: it turns out - that the earth for the ABS module was intermittent. Below the ABS pump on the firewall is a stud with 10mm nut and a couple of earth straps. WELL! The threaded stud is not threaded all the way down the stud. The nut on top was tight. (But it ran out of thread and it wasn’t clamping the earth strap’s loop connector very tightly at all. ) had to put a washer under it. And bingo. The high speed LAN was restored. Then I had to get dealer
To code the new ABS pump (module is inside that whole unit ) with 2 things. 1. The vin# and 2. The model car (cruze) those units go in 6 fm different cars and need to be told internally what model car it’s in. Now we are good again. Hope this helps you all.


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## popcorn4444 (Aug 13, 2021)

Azztheboy said:


> Hi Doug, (and every one else ). I wanted
> To report back what happened. So: it turns out - that the earth for the ABS module was intermittent. Below the ABS pump on the firewall is a stud with 10mm nut and a couple of earth straps. WELL! The threaded stud is not threaded all the way down the stud. The nut on top was tight. (But it ran out of thread and it wasn’t clamping the earth strap’s loop connector very tightly at all. ) had to put a washer under it. And bingo. The high speed LAN was restored. Then I had to get dealer
> To code the new ABS pump (module is inside that whole unit ) with 2 things. 1. The vin# and 2. The model car (cruze) those units go in 6 fm different cars and need to be told internally what model car it’s in. Now we are good again. Hope this helps you all.


Can you post a picture of where you located it???? I’ve been trying to find it myself to no avail! I’m having exact same isssues myself. Thank you


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## Ersin (10 mo ago)

plano-doug said:


> I think I can explain that. At each end of the line, there is a 120 ohm resistor. Together (ie, in parallel) they form 60 ohms of resistance. With the cables disconnected from the EBCM, the 120 ohm resistors on that end are removed, leaving only the resistors at the other end in the circuit.
> 
> Also, I think you should see 120 ohms between pins 10-12.
> 
> ...


Hello how are you my friend
cruze 1.6 petrol year 2010 simtec 76.1 ecu
i need your help i need chevrolet cruze ecu wiring diagram can you help me please
can i contact you
skype or whatsapp 

Thank you from now


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