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TL;DR - S-AWC system is commanding the AYC pump to try to make the car turn during WOT even though we are driving straight.

I have an interesting situation on a car here. It's got a big turbo kit and a built motor, so it makes some torque.

When I got WOT, the S-AWC display will indicate that it's sending extra power to opposing wheels (front left w/ rear right, or front right w/ rear left), which will make the car kind of shimmy back and forth in a terrifying manner. It feels like someone is grabbing the steering wheel and randomly steering it left to right, despite my desperate need to go straight.

In the midst of this tantrum, the dash will display the "ASC System Service Required" message.

This isn't caused by an overboost like it typically is, and I have that code disabled in the tune anyway.

I've experienced similar behavior in cars before (without the ASC message) and it would usually be something suspension related. Maybe a worn bushing that would flex too much under heavy acceleration and cause dynamic toe, for example.

This isn't the case here, and the suspension has been checked.

As a sanity check, if we pull the relay for the AYC, the issue doesn't occur. It will still throw the ASC message, but the car doesn't wiggle. Therefore, I'm assuming that the AYC pump is doing something to redistribute power and cause the car to dance around. No one leaves baby in the corner.

My best guess is that something that the SAWC system uses as an input is finicky, and the AYC computer is commanding the car to send power where it shouldn't.

We noticed that at idle the yaw sensor would randomly spike, so we replaced that with a used one to no avail.

We checked the steering angle sensor to make sure that straight ahead was ~0*, so it didn't think we were trying to turn while going straight.

We pulled the following codes from the system:

AYC/ACD computer:
C161D - AWC pump relay circuit
C1078 - Tire revolutions range


ABS computer:
C2204 - Sensor cluster internal error
U0100 - Engine CAN timeout
C1290 - Fail safe mode (lost of CAN data)

Most of which could be ignored since they were probably thrown while we were tinkering with things (pulling the relay likely caused C161D, for example).

However, the code that keeps coming back every time we do a pull is C2204.

The wheel speed sensors also seem to all be reading the same, so I don't think that's the issue.

Any ideas?
 

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TL;DR - S-AWC system is commanding the AYC pump to try to make the car turn during WOT even though we are driving straight.


We pulled the following codes from the system:

AYC/ACD computer:
C161D - AWC pump relay circuit
C1078 - Tire revolutions range


ABS computer:
C2204 - Sensor cluster internal error
U0100 - Engine CAN timeout
C1290 - Fail safe mode (lost of CAN data)

Most of which could be ignored since they were probably thrown while we were tinkering with things (pulling the relay likely caused C161D, for example).

However, the code that keeps coming back every time we do a pull is C2204.

The wheel speed sensors also seem to all be reading the same, so I don't think that's the issue.

Any ideas?
From the FSM

C2204 - Internal Abnormality in G and Yaw Rate Sensor

There are specific lights that will illuminate on the dash when this error pops up, which lights are displayed?

I'd follow the FSM diag tree, you'll want to start at page 174, linked HERE
 
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