Reduced Enging Performance - Code P0638

[zkc]

This morning my wife's 2004 2.5t AWD had two messages show up. "Reduced Engine Performance" and "Engine System Service Required" along with a check engine light. It would only limp along until after a couple or restarts and then the "Reduced Engine Performance" message disappeared but the other message and CEL stayed. I read the codes at a local auto parts store and it came up with P0638 - Throttle Actuator Performance Problem, Bank 1. I reset the codes and it's been ok since, but I'm sure it will probably come back when my wife is driving it... Any ideas of what to check???

Thanks for your help,
Zac:confused:

[Art]

The converted P-code 0638 reveals the following:


ECM-91A7 Throttle Unit

Condition
Diagnostic trouble code (DTC) ECM-91A7 is stored if the engine control module (ECM) registers, when the engine is running, that the required throttle angle (desired value) does not correspond with the actual throttle angle (actual value) in the throttle unit

Substitute value
The engine control module (ECM) shuts down the supply to the throttle unit damper motor. The throttle will set itself to the return position

Possible source

Faulty signal:
• The throttle is sticking or is blocked (oil film, dust etc.)
• Contact resistance or oxidation in the terminals between the engine control module (ECM) and the throttle unit
• Open-circuit, short-circuit to ground or short-circuit to supply voltage in the wiring for the damper motor in the throttle unit
• Short-circuit to each other in the wiring for the damper motor in the throttle unit
• Defective throttle unit.
Fault symptom[s]
• Malfunction indicator lamp (MIL) lit
• Poor performance.

[zkc]

Just wondering why this thread was moved to the XC70 thread. My car is a 2004 XC90 2.5t.

Thanks...

[Chilled Man]

Etm ?

[Art]

Just wondering why this thread was moved to the XC70 thread. My car is a 2004 XC90 2.5t.

Thanks...

Dunno...wasn't me. Back it goes then. :)