GM Low Speed Data Wires - Power Steering Issue with Speedo Loss

[Robinjo]

I would start with the standard high speed wiring test. 60 ohms at the DLC?

What is the DLC, that’s a new abbreviation to me. Edit: another name for OBD-2 port.

How would one perform this? Is it ad easy as pinning both HS wire coming into the DLC? Please be plain in the description as I’m not familiar with a lot of electric terms or slang.

 

[Gtstorey]

Search on here for “aeswave”. It will lead you to link I have posted multiple times for explanation of how high speed works and a basic test.

 

[Robinjo]

I’ll try that. I do remember seeing a sequence on taking things off the HS system to find the unit with an issue.

Edit: Adding here because a lot of the search items come up with the results ‘search for aeswave’.

https://resources.aeswave.com/ATG-05_Network-Diagnostics-and-Module-Programming.pdf#:~:text=High%20speed%20GMLAN%20uses%20two%20120%20Ohm%20termination,be%20less%20stable%2C%20and%20communication%20errors%20may%20occur

.

 

[Robinjo]

Search on here for “aeswave”. It will lead you to link I have posted multiple times for explanation of how high speed works and a basic test.

Issue came back and I have time to play with it. So I checked across the 6 and 14 pins on the DLC (OBD-2 port)

I get 60 Ohms across pin 6 & 14 with the key off.
With key on I get .2 Mega ohms (or I get 0.2 set on the 2 M Ohm setting). It's 'OL" on anything except the 2 M ohm setting.

Started pulling the main three off the system, all with out power connected. Each one of these is only disconnecting the the one item.
Disconnecting the BCM gives 120 Ohms.
Disconnecting the PCM gives 120 Ohms.
Disconnecting the small Power Steering plug gives OL.

Any advice in what this all is telling me? Or, next steps to try out?

 

[Gtstorey]

I don’t think that your results mean anything after you turn the key, I don’t think I’ve ever seen any values for key on.
Disconnect tests are what you should see, once you disconnect a module past the power steering, all you will see is the resistor in the PS.

I would guess that you have an intermittent failure in a module that pulls down the high speed. The most common failure seems to be the power steering. Other than changing it out, you need a full diagnostic scanner to see what is going on. And that might have to be while it’s failing.

I should still have my extra power steering if you want to try it. Unless I’ve already given it to you.

 

[Gtstorey]

If it was mine, I would probably start hunting down the correct Saturn Vue and the EPS controller from eBay and take the EPS out of the high speed chain and get better steering control.

 

[Desert Sasqwatch]

If going the extra step of locating a Vue EPS, versus replacing with a Cobalt EPS, get the variable controller for the Vue and set the power assist to the level that feels best.

Saturn Vue Chevy Equinox Electric power steering electronic controller box EPAS | eBay

This kit allow you to install Saturn Vue electric power steering to any other vehicle. Saturn Vue - from 2002 to 2007. Saturn Vue 2002 - 2007. In these steering columns the ECU (electronic box) is mounted in the steering column.

www.ebay.com

 

[Robinjo]

I should still have my extra power steering if you want to try it. Unless I’ve already given it to you.

I don’t think I did grab that. I’ll give it a try and then look at the Vue setup after getting back to running well.
It was intermittent and now it seems to be a constant failure.

 

[Gtstorey]

Found it. I may be in Huntsville this evening or fairly early Sunday morning.

 

[Robinjo]

Let me know and I’ll meet you

I see text faster. I think you have the number?

 

[Gtstorey]

Let me know and I’ll meet you

I see text faster. I think you have the number?

Not very good at keeping numbers. Send it to me.

 

[Robinjo]

New information, got a PS unit from GTStory and will try it today.

After trouble shooting yesterday, I had PS assist back but now nothing on the gauge cluster works. When starting the vehicle, the mileage comes on and the needles bounce a little. Then, they all die and only dashes come across the display where readout are typically (mileage also goes away). Previously I had mileage and the fuel/tach worked. Now, on the way from collecting the newer unit, PS assist stopped.

 

[Robinjo]

Swapped out the unit and still have the same condition.
Suggestions?

i should note that RPM’s do work on my Torque app and OBD2 plug. Fuel and speed do not.

 

[Gtstorey]

I would probably start checking the various connections at the bcm since it still runs and the bcm seems to act like the central data point.

or bring it my house and we will put a diagnostic scanner on it and see if that tells us anything.

 

[Robinjo]

Just for sanity I checked all the high speed data connections and got continuity across them.

OBD2 pin 6 to PS pin 1 (tan/black)
OBD2 pin 14 to PS pin 2 (tan)
PS pin 4 to BCM J2 pin 1 (brown/white)
PS pin 5 to BCM J2 pin 19 (brown)
BCM J2 pin 2 to PCM C1 pin 1 (tan/black)
BCM J2 pin 20 to PCM C1 pin 2 (tan)

anyone know the low speed wire pins to check?

 

[Markm]

Seems like you have a high speed issue with the cluster blanking out. Be certain to use micro 64 test terminals and be gentle with them as they’re pretty easy to spread and get poor contact. If there’s a chance you think you could have an intermittent broken wire I load test the circuits using a headlight bulb

 

[Gtstorey]

On the newer models, instrument cluster doesn’t connect to the high speed network. Probably doesn’t on the older models.

low speed doesn’t make a continuous circuit to the different points. Pin 1 of the DLC should connect to BCM, theft deterrent module and the instrument cluster. I think that is all of the modules that are retained. They were all tied together in the “comb” splice block cut out. It should be the dark green wire in those modules, but PIN number might be different in the older models.

 

[Gtstorey]

And not sure a load test on data wires will prove anything. Although I guess you could disconnect at both ends and load it that way. Current requirements on the data wires is so low that it should work even if mostly broken.

 

[Gtstorey]

And the nice thing about checking resistance on the high speed at the dlc is since one of the resistors is in the ECM at the end of the chain, it checks continuity of the entire circuit at once.

 

[Markm]

I was going off the top of my head on the high speed stuff but definitely seems like a communication issue. Load testing circuits confirms circuit integrity. Even though a circuit has continuity or even tests low on ohms doesn’t confirm it’s a good circuit. I test the circuits isolated