SureTrack Real Fix: Don’t Let The Cat Slow You Down

The owner of this Pontiac Grand AM complained that the check engine light was on for an EGR code. Upon further investigation it was found that there was also lack of power while driving. Follow this real fix to see how the diagnosis determined that it was a faulty catalytic converter causing the issues.

Vehicle
2003 Pontiac Grand Am SE 3.4L

Title
P0404, Replaced Catalytic Converter

Complaint
The customer states the check engine light is on.

Cause
Connected a scan tool and found code P0404 – Exhaust Gas Recirculation “A” Control Circuit Range/Performance. Used the scan tool to repeatedly command the exhaust gas recirculation valve open and closed, monitored the valve position parameters on the scan tool, and found the valve actual position parameter matched the valve desired position parameter. Performed a road test, used the scan tool to monitor live data and found the exhaust gas recirculation valve position parameter increased above 0% under heavy acceleration. The exhaust gas recirculation valve position parameter should have remained at 0% under heavy acceleration. Upon further inspection, also found the engine lacked power under heavy acceleration. Removed the oxygen sensor (B1-S1), connected a back pressure gauge to the oxygen sensor fitting, snapped the throttle and found the exhaust back pressure exceeded the maximum specification. Removed the exhaust after the catalytic converter and found the back pressure was still excessive, which indicated the catalytic converter was restricted. The excessive back pressure caused the exhaust gas recirculation valve pintle to open on heavy acceleration. These test results verified the catalytic converter was faulty.

Correction
Replaced the catalytic converter, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.