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2003 Mitsubishi Eclipse GS P0135 O2 Heater Circuit Fault: Diagnosis and Repair Guide

Model: 2003 Mitsubishi Eclipse GS Fault Code: P0135 Posted: 2011-04-09 16:37

I recently purchased an OBD2 scanner because my 'Service Engine Soon' light was illuminated, and it returned a diagnostic code: P0135 — O2 Sensor Heater Circuit Bank 1 Sensor 1. According to online resources, this code points to a faulty oxygen sensor heater circuit located on the front of the exhaust manifold in my 2003 Mitsubishi Eclipse GS with a 2.4L inline-4 engine (4G64). I replaced the sensor with a universal O2 sensor, cleared the code, but the P0135 code reappeared after restarting the vehicle. A pending P0135 code also appears in the system. Each time I clear the code, the 'Service Engine Soon' light flashes on every second start and remains illuminated until the next restart. Despite multiple attempts to reset the code, the issue persists. Can anyone provide insight into why this is happening? The persistent warning light is significantly impacting my daily driving experience.

Related fault codes
P0135
Comments (8)
Anonymous 2011-04-09 17:31

I used a universal O2 sensor as a replacement—could that be the root cause of the recurring P0135 code and illuminated service light?

Anonymous 2011-04-09 18:27

Is this a GS or GTS model? And what engine size? This information would help determine the correct diagnostic approach.

Anonymous 2011-04-09 18:42

It's a 2003 Eclipse GS with a 2.4L inline-4 engine.

Anonymous 2011-04-09 18:43

Engine code: 4G64.

Anonymous 2011-04-09 20:03

The O2 sensors in this model are often unreliable—replacing them with a genuine Mitsubishi OEM sensor should resolve the issue. I recommend visiting your local Mitsubishi dealership for an authentic part.

Anonymous 2011-04-09 20:13

Thanks for the advice—I'll check with a dealer to get the correct OEM sensor.

Anonymous 2011-04-10 12:43

Same as what Jeff mentioned—using original equipment manufacturer parts is key for reliable performance and code resolution.

Anonymous 2011-11-25 13:49

I have the same issue with my 2003 Eclipse 2.4L engine, which shares the same platform with the Dodge Stratus. I replaced both O2 sensors and spark plugs, but the P0135 code still appears when cranking. It's been six months—now the code has disappeared on its own. This worked for me; possibly a sensor or wiring issue was intermittent.