Loss of Power Steering and C0460 and C0895

[SonomaGTLS6]

Hi all - long story short, my wife got the Service Power Steering message while at work yesterday and lost assist while backing out of a parking spot (2011 Yukon Hybrid with 130k miles). Multiple ignition cycles since leaving home that morning and it failed at lunch time. She thinks it failed at full lock while backing out of the spot (was able to turn the wheel all the way when backing up but when going forward could not turn the other direction). Disconnected battery, read and cleared codes, no luck. Charged the 12V battery overnight (battery is 2-3 years old) and showed good voltage when starting up this morning, issue still persists and I was able to get the codes to come back. No fuses blown. The C0460 (Steering Position Sensor Malfunction - Current) and C0895 (Device Voltage Malfunction - History) are present in the PSCM.

My first question is does the C0460 indicate the steering angle sensor is bad within the EPS or is that the SAS at the base of the steering column on the lower shaft? No stabilitrak or ABS codes and I drove the truck home with manual steering a good 15 miles from wife's workplace so I'm inclined to believe this is within the EPS.

Did a search for the C0460 online and don't see much...also have not seen anything specific on the Hybrid forums here and elsewhere. Thanks for any help that can be offered!

 

[SonomaGTLS6]

Here is a video of the noises coming from the EPS unit. engine off and engine running.

Only concerning noise I hear engine off is what sounds like a bearing squeal. The more consistent gravely noise I’m fairly certain is the freewheeling recirculating ballnut.

Engine on there is the squeal and an odd low frequency zipper noise. You can feel the zipper vibration in the steering wheel as well.

 

[SonomaGTLS6]

Update - i pulled the motor yesterday and it's a broken motor shaft. Very interesting considering the noises coming from the system when power is on vs. power off.

 

[Doubeleive]

Update - i pulled the motor yesterday and it's a broken motor shaft. Very interesting considering the noises coming from the system when power is on vs. power off.

so what the hell happens when it breaks like that going down the road, no steering at all? or just hard to steer?

 

[SonomaGTLS6]

so what the hell happens when it breaks like that going down the road, no steering at all? or just hard to steer?

It was loss of power assist...so manual steering going down the road, akin to having a power steering pump go out on a hydraulic system. Not too bad at higher speeds but 5mph and below very difficult. It would be a challenge to do an evasive maneuver if you pulled out into traffic at the wrong time.

Ended up replacing the motor and everything is working fine. Also found an alternative way to diagnose the broken shaft in vehicle using the 3 phase motor regen current. Video for future reference:

 

[BG1988]

so what the hell happens when it breaks like that going down the road, no steering at all? or just hard to steer?

a crash most likely if it happens when driving

 

[dnt1010]

Awesome diagnostic check for a broken motor shaft without throwing parts at a problem or doing a bunch of disassembly. A+ video, thanks for sharing.