Diagnostic Aids

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

If a TP sensor 1 or 2 DTC is set, diagnose that DTC first.

If DTC P1551 is set, the ECM will default to one of the two limp home modes (random injector disable with engine speed limited to 2600 RPM). The REDUCED POWER telltale will be illuminated and the ECM will remain in this condition for the entire ignition cycle even if the fault is corrected.

Possible causes of DTC P1551:

Weak throttle body return springs or throttle plate sticking.
TP sensor 1 or 2 skewed or resistance in the wiring.

To test for a skewed TP sensor 1 or skewed TP sensor 2, see DIAGNOSTIC AIDS under DTC P0121: TP SENSOR NO. 1 CIRCUIT PERFORMANCE.