Test TC-11A - Oxygen Sensor (O2S) Stays Below Center (Lean) (DTC 51)
WARNING: This page is about a different car, the 1995 Jeep Wrangler, 1995 Jeep Grand Cherokee, and 1995 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Perform TEST TC-1A
before proceeding with this test. For connector terminal identification, see CONNECTOR IDENTIFICATION
at beginning of article. For wiring diagrams, see WIRING DIAGRAMS
at the end of this article. Perform TEST VER-2A
after each repair.
- Start engine and allow to run until normal operating temperature is reached. Using scan tool, set engine speed to 1500 RPM. Using scan tool, read O2S voltage. If O2S voltage is not always less than .5 volt, stop test and go to next step. If O2S voltage is always less than .5 volt, go to step 3).
- Condition required to set trouble code message is not present at this time. O2S STAYS BELOW CENTER (LEAN) trouble code message sets if O2S output voltage stays at less than .5 volt without changing for more than 8 minutes. Possible causes are: vacuum leak, low fuel pressure, other engine sensor calibration failures, ignition system failure, O2S failure or mechanical engine problem. Correct any defect listed as possible cause and retest.
- Using scan tool, check if O2S voltage is always at or less than 0.1 volt. If O2S voltage is always at or less than 0.1 volt, go to next step. If O2S voltage is not always at or less than 0.1 volt a condition causing engine to run lean is present. Go to TEST NTC-1A .
- Using scan tool, stop all actuation tests. Turn ignition on with engine off. Disconnect O2S connector and ensure connector is clean and not damaged. Using scan tool, read O2S state. If O2S state is not at center, go to next step. If O2S state is at center, replace O2S.
- Turn ignition off. Disconnect Powertrain Control Module (PCM) connector and ensure connector is clean and not damaged. Using scan tool in ohmmeter mode, check resistance of O2S connector (harness side), signal circuit (Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire on ZJ body). If resistance is less than 5 ohms, repair short to ground in O2S signal circuit. If resistance is more than 5 ohms, replace PCM.