P0172

DIAGNOSTIC TROUBLE CODES P0171, P0172/P1172, P1173
Incorrect fuel-air mixture, adaptation lean or rich/,
Air flow when idling, adaptation towards closed (lean) or open (rich).

Fault Symptom.
CHECK ENGINE lamp (MIL) on.

Condition
P0171, PO172:
More than 25% richer or more than 25% leaner for at least 60 seconds,
P1172, P1173:
Air flow rate through the Idle Air Control (IAC) valve when idling too low or too high in relation to the expected flow rate.

Diagnostic Procedure.
If other diagnostic trouble codes are present, deal with them first.
1. Clear all trouble codes and drive the car to check whether any trouble codes are generated afresh.
If they are, continue as described below.

2. Check the following points:
- that components of the correct type are fitted in the fuel system
- that no air leakage occurs in the air induction system (paying special attention to the 0-rings)
- that fuel pressure is correct
- that battery voltage is correct
- that no leakage occurs in the exhaust system ahead of the oxygen sensor
- that all grounding points in the system are OK

3. If no faults can be detected after carrying out the above checking procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh.

If they are, continue at "Before Control Module Replacement" for further diagnostic instructions. Before Replacing A Control Module