CUSTOMER CONCERN Customer states the check-engine light is on. DTC P0420 is stored. CAUSE Exhaust-manifold, misfire, coolant-consumption and fuel-trim checks confirmed the catalytic converter was below efficiency. CORRECTION Remove and replace catalytic converter. Clear DTC P0420 and verify catalyst-monitor operation.

CUSTOMER CONCERN Customer states the engine idles too high after the throttle-body bore was cleaned. No DTCs are stored. CAUSE Throttle-body cleaning changed the effective airflow at the learned throttle position, leaving the idle adaptation out of range. CORRECTION Perform idle-learn reset with a compatible scan tool. Verify commanded and actual idle speed.

CUSTOMER CONCERN Customer states the malfunction indicator light is on, the engine surges at idle and raw fuel odor is present. DTC P0171 is stored. CAUSE Testing with the front oxygen sensor isolated confirmed an exhaust leak from a cracked exhaust manifold was altering fuel-control feedback. CORRECTION Remove and replace exhaust manifold. Repair exhaust leaks, clear DTC P0171 and verify stable idle operation.

CUSTOMER CONCERN Customer states the brake lights intermittently remain on. DTCs C0561 and C0161 are stored. CAUSE Brake-booster alignment caused incorrect brake-switch operation, confirming a misadjusted booster-to-cowl mounting position. CORRECTION Remove brake booster, install specified spacing washers on the booster studs and reinstall booster. Clear brake DTCs and verify brake-light operation.

CUSTOMER CONCERN Customer states the vehicle intermittently will not crank or start. DTC P0601 repeatedly returns. CAUSE PCM power and ground circuits tested correctly, confirming an internal memory fault in the Powertrain Control Module. CORRECTION Remove and replace Powertrain Control Module. Program module with current calibration, perform crankshaft-position variation relearn and clear DTC P0601.