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98 Mitsubishi Montero Sport P0141 O2 Sensor Heater Circuit Fault - Diagnosis and Fix

Model: 98 Mitsubishi Montero Sport Fault Code: P0141 Posted: 2011-08-25 00:35

I recently purchased a 1998 Mitsubishi Montero Sport (3.0L, 4x4, 175,000 miles) for my dad. The vehicle has several issues that need addressing before regular use. I replaced the oxygen sensor and cleared the fault code P0141. After allowing it to idle and moving it a few feet, the code returned. This suggests a possible short in the heater circuit or wiring. The O2 sensor is located just after the two exhaust pipes merge into one. It appeared clean externally, with only slight blackening upon inspection. Despite this, I replaced it as a precaution. I also previously saw P0170 (fuel trim issue), but that code has not returned since. Since I don't have access to a Chilton or Haynes manual for this model, locating the wiring diagram is proving difficult. I'm seeking help identifying the correct sensor location and diagnosing potential electrical faults in the heater circuit. I will update my progress and final conclusion as I continue troubleshooting.

Related fault codes
P0141
Comments (4)
Anonymous 2011-08-25 05:00

I'm doubtful that a 1998 Mitsubishi Montero Sport only has one oxygen sensor. It's possible you replaced the wrong sensor or used a low-quality brand—both could be contributing factors.

Anonymous 2011-08-25 11:06

The P0141 code specifically indicates an 'Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)'. This means the vehicle has multiple O2 sensors. You may have mistakenly replaced Sensor 1 instead of Sensor 2. The area after Sensor 2 is only connected to the muffler and tailpipe. Regarding sensor quality—while a cheap sensor might not perform well, it's unlikely that a brand-new one would fail immediately. Still, it's worth considering compatibility and proper installation. I'm checking a few known issues today for possible short circuits. I’m not very experienced with electrical systems, but hands-on troubleshooting is the best way to learn!

Anonymous 2011-09-01 14:54

Oh man—I found Sensor 2 today! It was right in an open location near the muffler. I replaced it with a new one. After this change, the P0141 code has not returned. If no further issues arise within the next month as I begin regular driving, this fix appears to have resolved the problem. Note: A user on a Montero Sport forum suggested testing sensor resistance. I tested the new sensor and got 16 ohms—matching the reading from the original good sensor. The faulty one read 0 ohms. This suggests that a failed sensor or poor connection may be causing the heater circuit malfunction.

Anonymous 2011-09-01 19:36

Yes, if the heater circuit opens when it should be closed (especially as temperature rises), this is a common issue and can trigger P0141. A properly functioning sensor must maintain resistance as it heats up—any open or unstable behavior will cause the code to appear.