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Oil Pressure Gauge Operating Improperly

NOTE: For more information, see Technical Bulletin FALSE LOW OIL PRESSURE GAUGE READING No. 87-C-3, dated 4/1/87 in the TECH SERVICE BULLETINS section.
  1. Enter diagnostics and check if BCM diagnostic codes B131 and/or B132 are set. If codes B131 and/or B132 are set, proceed to next step. If no codes are set, proceed to step 7).
  2. With ignition on and engine off, enter diagnostics and select BCM data BD71. This should display oil pressure (psi). If display indicates below 10 psi, fault is not present.
    NOTE: If vehicle was originally equipped with a pressure switch and a code B132 was set, replace switch with a sensor or install a new switch and have EEPROM reprogrammed for a switch.
  3. If display indicates 10 psi or above, connect a jumper from oil pressure switch terminal "A" (Light Green wire) to terminal "B" (Black/Pink wire) and note data value. If display indicates below 10 psi, replace oil pressure sensor.
  4. If display indicates 10 psi or above, ground circuit No. 313 (Light Green wire) by connecting jumper to ground, as described in step 3), and note data value. If display indicates below 10 psi, repair open in circuit No. 736 (Black/Pink wire).
  5. If display indicates 10 psi or above, backprobe BCM from terminal 3D9 to ground and note data value. If display indicates below 10 psi, repair open in circuit No. 313 (Light Green wire).
  6. If display indicates 10 psi or above, check for poor contact at BCM terminal 3D9. If contact is okay, replace BCM.
    Fig 1: Oil Pressure Sensor Connector & Circuit ID Chart
    G8244Courtesy of GENERAL MOTORS CORP.
  7. Determine if engine has a high or low oil pressure condition by removing oil pressure sensor. Connect a known good mechanical oil pressure gauge to check pressure.
  8. If gauge indicates that engine has a low or high oil pressure condition, IPC is not at fault. If gauge indicates that pressure is normal, proceed to next step.
  9. Unplug oil pressure sensor. With ignition switch in "RUN" position, connect a voltmeter between terminal "A" (Light/Green wire) and ground. Voltmeter should indicate 5 volts. If 5 volts is not present, proceed to step 11).
  10. If voltmeter indicates 5 volts, connect voltmeter between terminal "A" (Light/Green wire) and terminal "B" (Black/Pink wire.) If 5 volts is present, replace oil pressure sensor. If 5 volts is not present, check and replace Black/Pink wire.
  11. Backprobe terminal 3D9 of BCM to ground, using a voltmeter. If 5 volts is present, check and repair Light/Green wire.
  12. If 5 volts is not present, check connections. If connections are good, replace BCM.
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