Steering Assist Reduced Issue

Towerhog · August 11, 2017

OK. 2017 LTZ 6.2L DC. Had an issue with Steering Assist Reduced Drive With Care message. First of June I get the message, took to dealer, they looked at it, said it was a ground block issue. Checked the ground blocks indicated by the DTC's and found no issues. Deleted the codes. Truck returned.

A week goes by and the message appears again while driving. The truck goes into limp mode. Shut the truck off, restarted. message still there but no issues with transmission driving to the dealer. This time I had transmission codes as well. They took the truck for a week and re-secured the ground blocks with star washers then test drove off and on for that week. Codes are gone.

Today. Got the message last Saturday. Got to the dealer yesterday. They kept it over night and called today to say that they had found the most probable problem with the system. Turns out they found BCM codes in every module. They cleared the codes but one was persistent. The license plate circuit. It kept showing a high voltage draw. I had installed LED bulbs for the license plate about 10 months ago with no issues (or so I thought). They replaced the LED bulbs with the OEM bulbs and VIOLA!! The codes did not reappear. The service writer said they cant be certain that was the cause of the message, but the codes had not retuned since the LED bulbs removal.

So I guess LED bulbs do go bad. Who knew. The dealer said they would eat the cost of this one even though the possible cause were aftermarket bulbs.

Edited August 11, 2017 by Towerhog

newdude · August 11, 2017

Shows you how PMS these newer vehicles can get LOL. Good to see the dealer helped you with it.

Towerhog · August 14, 2017

Looks as though the bulbs weren't the problem. Got message again on Sunday. Goes back in to the dealer Wednesday.

sk · August 14, 2017

Known problem. Search these forums for "electrical issues". There is a TSB with 4 or 5 things the tech is supposed to check (should be PIT5405 attached in one of those threads). Positive battery cables, positive connection to starter, but most importantly the G218 ground for the BCM. I had the same issues with lots of codes and my dealer couldn't fix it. Once I found the TSB on these forums I checked the ground myself (easy to do and takes about 20 minutes). Since I fixed the ground I have not had any issues.

Edited August 14, 2017 by sk

Towerhog · August 15, 2017

Known problem. Search these forums for "electrical issues". There is a TSB with 4 or 5 things the tech is supposed to check (should be PIT5405 attached in one of those threads). Positive battery cables, positive connection to starter, but most importantly the G218 ground for the BCM. I had the same issues with lots of codes and my dealer couldn't fix it. Once I found the TSB on these forums I checked the ground myself (easy to do and takes about 20 minutes). Since I fixed the ground I have not had any issues.

Thanks. They did check and tighten (cleaned ground contacts and used star washers to ensure good contact with frame). They indicated they did the G107, G121, G400 and G101 per GM's diagnostics. They didn't mention the G218 point. The dealership was referred by GM Tech Assist to GM Doc 4778218, 4372049, 4775768 for electrical diagnostics. Ill let them check it out this week and see what they come up with. After it comes back Ill crawl under with my service manuals and check the ground blocks, especially G218.

sk · August 21, 2017

Thanks. They did check and tighten (cleaned ground contacts and used star washers to ensure good contact with frame). They indicated they did the G107, G121, G400 and G101 per GM's diagnostics. They didn't mention the G218 point. The dealership was referred by GM Tech Assist to GM Doc 4778218, 4372049, 4775768 for electrical diagnostics. Ill let them check it out this week and see what they come up with. After it comes back Ill crawl under with my service manuals and check the ground blocks, especially G218.

You don't have to crawl anywhere to check the G218 ground:

1) Remove A-pillar trim pieces.

2) Pry up the front part of the dash trim (the dash is split near the windshield and defroster vent).

3) Optional -- remove the tweeters for easier access.

4) Remove the ground nut near the front corner. Clean under the nut, around the stud base, and make sure the dash insulation is not pinched. The G218 ground is on the driver's side but I did the one on the passenger side while I had the dash open.

5) Replace everything.

Takes about 20 minutes total while you are sitting in your garage or driveway ...

SilveradoSaver · August 21, 2017

Known problem. Search these forums for "electrical issues". There is a TSB with 4 or 5 things the tech is supposed to check (should be PIT5405 attached in one of those threads). Positive battery cables, positive connection to starter, but most importantly the G218 ground for the BCM. I had the same issues with lots of codes and my dealer couldn't fix it. Once I found the TSB on these forums I checked the ground myself (easy to do and takes about 20 minutes). Since I fixed the ground I have not had any issues.

Sad that you had to find the TSB and do this versus the dealership...

Towerhog · August 22, 2017

Got truck back this morning. Faults again cleared. Found 3 codes in system U0140 Loss Comm with BCM, U0121 Loss Comm with ECM, U0100 Loss Comm with EBC. They separated connections for all control modules, inspected for dent or damaged pins. Then added Electric grease and re-secured all connections.

We'll see what happens this time.

As for the G218 ground. They did that on the first service. Appreciate the info.

Htown_LTZ · April 17, 2018

HELP! So I recently installed aftermarket tow mirrors on my 2017 Z71 LT. When I went to turn it on to check if everything was working, this message popped up "steering assists reduced. Please drive carefully" I checked all my wiring and everything seems to be fine. Anybody have any idea why this is happening? Any input would he greatly appreciated.

adailey · August 26, 2018

On 4/17/2018 at 6:13 PM, Htown_LTZ said:

HELP! So I recently installed aftermarket tow mirrors on my 2017 Z71 LT. When I went to turn it on to check if everything was working, this message popped up "steering assists reduced. Please drive carefully" I checked all my wiring and everything seems to be fine. Anybody have any idea why this is happening? Any input would he greatly appreciated.

i have the same issue. Got some mirrors from boost auto parts and installed with no issues. Now im getting this code.

Htown_LTZ · August 26, 2018

Well, I took mine off earlier today. It was a hassle getting in and out of my garage/carport. Maybe taking them off will remove that code.

adailey · August 27, 2018

1 hour ago, Htown_LTZ said:

Well, I took mine off earlier today. It was a hassle getting in and out of my garage/carport. Maybe taking them off will remove that code.

I really don’t wanna take them

off since I paid over 400 for them.

Htown_LTZ · August 27, 2018

I paid $160 for mine. They worked just as good as OEM.

Tahoe02 · August 27, 2018

Check with pgamboa on this forum that makes all the wiring harnesses for all the upgrades including mirrors. He has plenty of posts on here and should be easy to find.