1998 Mitsubishi Galant O2 sensor problems

Tiny
BDIEDRICH97
  • MEMBER
  • 1998 MITSUBISHI GALANT
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,575 MILES
The check engine light was on and a scan revealed that there was an [O2 sensor heater circuit malfunction (Bank 1, Sensor, )] which is the upstream sensor as I have been informed. That sensor has been replaced twice. I have also reset by disconecting the batery and cleared the the code with a state inspection computer. Other maintenance performed in an attempt to correct the problem includes cleaning the spark plugs and putting fuel system cleaner into gas tank. Yet the check engine light continues to come back on.
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Monday, July 19th, 2010 AT 9:44 AM

3 Replies

Tiny
KHLOW2008
  • EXPERT
Hi bdiedrich97,

Let me know the exact trouble code and I will get the diagnostic procedures for you.
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Monday, July 19th, 2010 AT 11:48 AM
Tiny
BDIEDRICH97
  • MEMBER
The code is P0135
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Monday, July 19th, 2010 AT 12:42 PM
Tiny
KHLOW2008
  • EXPERT
DTC P0135: FRONT HEATED OXYGEN SENSOR (HO2S) HEATER CIRCUIT MALFUNCTION

1. Disconnect front Heated Oxygen Sensor (HO2S) connector. Connect Test Harness (MD998464 ) to front HO2S. Check continuity between ground and test harness terminals No. 1 (Red clip) and No. 3 (Blue clip) on Eclipse and Galant (California), or terminals No. 2 (Red clip) and No. 4 (Blue clip) on Galant (Federal). If continuity exists, go to next step. If continuity does not exist, replace front HO2S.

2. Start and warm engine until engine coolant temperature is 176 F (80 C) or more. Connect jumper wires between battery voltage and test harness terminal No. 1 (Red clip) and between ground and terminal No. 3 (Blue clip). Connect DVOM between test harness terminals No. 2 (Black clip) and No. 4 (White clip) on Eclipse and Galant (California), or terminals No. 1 (Black clip) and No. 3 (White clip) on Galant (Federal). Check front HO2S output voltage while repeatedly racing engine. If voltage is 0.6-1.0 volt, go to next step. If voltage is not as
specified, replace front HO2S.

3. Disconnect test harness. Turn ignition on. Check voltage between rear HO2S connector terminal No. 1 on Eclipse 2.0L and Galant (California), or No. 2 on Eclipse 2.4L and Galant (Federal). If battery voltage exists, go to next step. If battery voltage does not exist, check PCM connector and wiring harness between front HO2S connector and PCM.

4. Disconnect PCM connector. Turn ignition on. Check voltage between ground and PCM connector terminal No. 60 on Eclipse, or No. 90 on Galant. If battery voltage does not exist, check connectors and wiring harness between front HO2S connector and PCM. If battery voltage exists, check PCM connector. If PCM connector is okay, replace PCM.
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Monday, July 19th, 2010 AT 1:02 PM

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