6G72 Engine Codes P0175/P0171/P0134/P0135/P0340/P0335 - 2002 Eclipse GT (201k miles) Idle Drops to 400 RPM
My 2002 Eclipse GT (6G72 engine) has recently triggered multiple diagnostic trouble codes: P0175 (running too rich on bank 2), P0171 (running too lean on bank 2), P0134 (oxygen sensor no activity on bank 1), P0135 (oxygen sensor malfunction on bank 1), P0340 (camshaft position sensor malfunction), and P0335 (crankshaft position sensor malfunction). The vehicle still runs smoothly with good torque, decent fuel economy, and a stable idle under normal conditions. However, I've noticed that when the clutch is engaged, the idle will occasionally drop to around 400 RPM — and in rare cases, it has stalled during this condition. This issue only appears after clearing the codes, and the engine returns to normal operation shortly afterward. The codes reappear within five minutes of clearing. I've confirmed that the timing belt is properly aligned with all marks in place. The car is equipped with a budget catalytic converter, which may be contributing to emissions-related sensor inaccuracies. Given these symptoms and the recurring fault codes, I'm wondering if there's a known issue or potential fix for this combination of errors on the 6G72 engine platform? Any insights from owners of similar vehicles would be greatly appreciated.
With multiple sensor-related codes such as P0340 and P0335, it's critical to inspect the wiring harnesses and electrical connections for those sensors. A poor ground or intermittent signal could cause false readings and trigger both the crank and camshaft position faults. Additionally, check for voltage drops in the O2 sensor circuits — especially given the P0134 and P0135 codes — as a faulty or degraded catalytic converter may interfere with sensor feedback loops.