2011 STS with intermittent p/s increased effort

[cdgrinci]

Okay, let me give this a go. I have a 2011 STS that has been practically trouble free, and even the problem I am about to describe, is intermittent (I know, not good).

Occasionally the effort of my power steering increases, not gone, but increased; it seems as it is performing as it would at hwy speeds (reduced assist and resistance to self-centering). I took it to the dealer and explained the problem; they inspected it and said they couldn't find any problem (well, I was afraid of that because the morning I took it in the steering was working).

It happened again this morning, and through the course of the morning, sorted itself out and began working again. It may be a 'warm-up' thing, but since it just looses the slow speed/parking assist mode, I'm thinking not. Any help would be appreciated.

If it gets more consistent I'll head back to the dealer but until it does there's not need for the trip.

Thanks,

Chuck

[Cadillac Jim]

Ask OnStar to run the OBD codes and post them here. There are a number of Cnnnn codes on the variable effort steering.

Looking at the 2011 FSM, the hydraulics look pretty simple. The dealer probably checked for belt slippage, low or bad fluid, pump performance, and the other things that represent the FSM procedures for checking out the PS system. It wouldn't hurt to check the PS fluid for proper level, appearance, and smell.

If you have varible effort steering (RPO NV7), things are pretty simple. The variable effort actuator is on the steering rack, and has a connector with two wires: GY and WH. The low-effort signal comes through the WH wire. These wires go only to the EBCM. I would check the serpentine belt for slipping (smell of hot rubber or plastic), and check the connector and wiring, particularly the WH wire near and at the connector to the steering rack.

If you have the Active Front Steering Module and Actuator (RPO JL7), you still have a variable effort actuator on the steering rack but it will be different from the NV7 actuator. And, you will have a Power Steering Control Module (PSCM) that has a seven-wire connector to the Upper Intermediate Steering Shaft. Check for a cracked or bad 30 Amp AFS fuse in the underhood fuse block, a cracked or bad 10 Amp RIM/RPA/ISRVM/CLM fuse in the right rear fuse block. It's hard to imagine wiring problems relating to the PSCM causing issues without throwing a code, so a HISTORY code of the form Cnnnn might be there somewhere.

[cdgrinci]

Thanks Jim, good info.

[MAC]

Chances are it's the power steering pump. Maybe not, but I do know that the STS models have issues with pumps going bad. I replaced the pump on my '05. Not the easiest job, but not impossible for the average home mechanic. If fluid is good and the belt is not slipping then I suspect the pump, especially if steering becomes difficult and stays that way.