It was truly reading 0 ohms, it should have some amount of resistance, even if it's just 2 or 3 ohm...I will try with a different meter today. I also attempted to measure phase-phase AC voltage while back driving the gear (battery unplugged) and it never registered a regenerative voltage.

I also measured them to chassis ground and got no continuity so if the meter is correct the phases themselves are shorted together.

Putting two and two together I think the voltage DTC that popped up on the PSCM may be related to overcurrent going to the motor. There is a comment I read somewhere online that if you get the C0895 "Voltage Malfunction" on the PSCM it could indicate overcurrent. I hope the PSCM has protections built in to avoid damage during output shorts, but I am figuring the next step after replacing motor will be to replace the PSCM and 42V module

 

When I measure across each phase I am getting 30-40 mOhm on a new meter, no shorts to ground on either. This would make more sense considering the motor windings are probably thick gauge.

 

Additionally I probed for AC voltage across the phases again with this meter while articulating the road wheel and did not measure any back drive regen voltage.

So if the 40mohms is good on the windings, this would suggest the motor shaft is not turning (broken). It still does not explain the change in noise/handwheel cogging when the truck is running and should be providing assist (vs power off).

 

is it getting anything on the 42volt module output? i .e 42 volts


also does it beep on the conductivity setting on the muti meter?

 

I did not measure the 42V output, but when I unplugged the motor and started the truck to move it I got a new code for an internal failure (assumed because the motor was unhooked/not drawing current). Also got the beep with the continuity check.

Later this afternoon I removed the existing motor…lo and behold it’s a broken shaft. When I get the new motor on hand I will check if there is a regen voltage across phases at all when spinning it (there should be an AC voltage even at very low RPM). This check might prove useful for someone in the future to identify if the shaft is broken without removing the motor.

 

it will still have some voltage on the output side for a moment

i would buy a used replacement this rig is not worth spend 600-700$ for the new replacement motor get one from a pick a part place

 

I ended up finding a full new REPS assembly from a car parts place on eBay for $750 shipped. Figured I will just take the motor off this and keep the gear around for anything in the future. Effectively getting the mechanical unit for free with this.

 

save the old motor. don't throw it away
also be sure to file a report with the NHTSA...
Report a Vehicle Safety Problem, Equipment Issue | NHTSA

 

Did the motor replacement and everything works great! No position codes or anything, return to center/assist balance feels fine.

One other thing I realized while fixing this is you can diagnose the broken motor shaft in vehicle, without removing the motor. Instead of probing for resistance in the motor to check for shorted phases, if you measure AC voltage across two of the phases and back drive the system (while batteries unplugged) you will get a regen voltage on a good motor. My original motor in the truck had no regen whatsoever indicating the mechanical link between the gear and motor was broken.

Here's a little video for future reference: