Test TC-9A - O2S Stays Below Center (Lean) (DTC 51)

WARNING: This page is about a different car, the 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagrams, see WIRING DIAGRAM section.

Start engine and apply parking brake. Using scan tool, set engine speed to 1500 RPM. Using scan tool, read Oxygen Sensor (O2S) voltage. If O2S voltage is not always less than .5 volt, condition required to set DTC is not present at this time. Go to next step. If O2S voltage is always less than .5 volt, go to step 3).
O2S STAYS BELOW CENTER (LEAN) DTC sets if O2S output voltage stays less than .5 volt without toggling for at least 8 minutes. Possible causes are: low fuel pressure, vacuum leak, other engine sensor calibration failures, ignition system failure, O2S failure or mechanical engine failure. Go to TEST NTC-1A.
Using scan tool, check if O2S voltage is always at zero volts. If O2S voltage is always zero volts, go to step 5). If O2S voltage is not always zero volts, check O2S connector for excessive dirt and/or grease build-up. Closely check O2S connector Black/Dark Green wire for tracking to O2S connector Black/Tan wire and Black/Light Blue wire.
If excessive dirt and/or grease build-up is present, clean O2S connector as necessary. Perform TEST VER-2. If excessive dirt and/or grease build-up is not present, a condition causing engine to run lean is indicated. Go to TEST NTC-1A.
Using scan tool, stop all actuation of vehicle components. Turn ignition on with engine off. Disconnect O2S connector. Using scan tool, read O2S voltage. If O2S voltage is always .5 volt, replace O2S. Perform TEST VER-2.
If O2S voltage is not always .5 volt, turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Put scan tool in ohmmeter mode. Using scan tool, check resistance of Black/Dark Green wire on O2S connector.
If resistance is less than 5 ohms, repair short to ground in Black/Dark Green wire. Perform TEST VER-2. If resistance is more than 5 ohms, replace PCM. Perform TEST VER-2.