P0172

Read the instructions below then start the fault diagnostic procedure.

Symptom: CHECK ENGINE goes on after two driving cycles. Engine may stop straight after starting, run unevenly and misfire.

P0172

Fault symptoms

•	CHECK ENGINE goes on after two driving cycles.

•	Engine may stop straight after starting, run unevenly and misfire.

Conditions

The following conditions apply for this DTC:

•	Engine running and closed loop active.

•	Multiplicative adaptation below -25 % for more than 30 s.

Diagnostic help

The engine's fuel requirement is 25% less under partial load than that which the control module has calculated using information from the mass air flow sensor.

Fault diagnosis first determines if the pressure sensors indicate about the same value with the ignition ON, as the mass air flow sensor is then compared with the intake air pressure. If the pressure sensors are OK but the mass air flow sensor value is not correct, then air leaks between the compressor and the throttle are checked for first and then the mass air flow sensor is changed.

If the air quantity is OK, then the fuel supply is checked, i.e. pressure, response, pump flow and finally the injectors.

Functions in the diagnostic tool related to the fault:

•	Multiplicative Adaptation, unit %

•	Closed loop, unit %.

•	Purge Adaptation, unit %.

•	Air mass deviation from calculated, unit %.

See also description of test readings, , for more information.

Checking the wiring

Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits. Observe the multimeter, diagnostic tool or test lamp during the check.