Oil Pressure Gauge - Erratic or Becomes Inoperative
91ford29
Article No.
91-25-9
12/13/91
INSTRUMENT CLUSTER - ANALOG - OIL PRESSURE GAUGE INACCURATE, INOPERATIVE OR ERRATIC OPERATION - VEHICLES BUILT FROM JOB # 1 THROUGH 12/31/88
FORD: 1989 PROBE
ISSUE: The oil pressure gauge may not register accurately, be erratic or become inoperative. This may occur because of a failure in the oil pressure jumper wire harness.
ACTION: If service is required, refer to the following procedure for additional diagnostic and service details. Refer to TSB 90-14-9 for a list of parts by the production date of the vehicle. Refer the 1989 Probe Shop Manual, Pages 33-01-11/13, for basic oil pressure gauge diagnosis information.
1. Determine the type of oil pressure gauge condition.
^ Erratic operation
^ Inaccurate readings
^ Inoperative.
2. Install a mechanical "test" gauge and check for correct engine oil pressure at 1000 RPM (21-36 psi) and 3000 RPM (43-57 psi). If OK proceed to Step 3.
3. Perform all diagnostic procedures outlined in the 1989 Probe Shop Manual, Pages 33-01-11 through 33-01-13. Repair or replace components as needed. Refer to the parts block for correct parts usage.
4. If all components and wiring test OK, install a Rotunda Instrument Gauge Tester 021-0055, or equivalent and follow the instructions.
NOTE: IF THE GAUGE REGISTERS CORRECTLY, USING THE ROTUNDA INSTRUMENT GAUGE TESTER, THE CAUSE OF THE INACCURATE GAUGE COULD BE THE JUMPER HARNESS.
5. Determine the build date of the vehicle. The build date is located on the certification label on the driver's side door jamb. If the vehicle was built between February 1988 and December 1988, proceed to Step 5. If the build date is January 1989 or later, refer to TSB 90-14-9.
NOTE: REFER TO THE REVISED ELECTRICAL SCHEMATIC, FIGURE 1. EARLY BUILT PROBE VEHICLES HAD AN OIL PRESSURE JUMPER HARNESS (RESISTOR AND DIODE) ADDED DURING PRODUCTION. IT IS ATTACHED TO THE LEFT FENDER BETWEEN THE BATTERY AND THE VANE AIR METER HOSE.
6. Untape the resistor and diode. Inspect for damage or corrosion.
CAUTION: PLEASE NOTE THE WAY THE PARTS ARE ASSEMBLED. THE RESISTOR AND THE DIODE HAVE IDENTICAL CONNECTORS AND WHEN DISASSEMBLED COULD BE REINSTALLED IN THE WRONG CONNECTOR.
7. Disconnect the resistor from the harness. Use an ohmmeter to check for approximately 620 ohms resistance. Test the diode for correct circuit operation/polarity. If either part has failed, use the parts listed in this TSB.
8. If the diode and or resistor are OK, check for a damaged wire harness.
a. Isolate the harness from the ECA, the idle switch, oil pressure sender and the gauge.
Figure 1:
b. Test for continuity, correct wire colors, connectors and splice locations. Refer to the wiring schematic in Figure 1.
9. Repair the wires and connectors as needed, then reinstall the diode and resistor in their respective connectors.
10. Recheck the operation of the oil pressure gauge.
The oil pressure sender units for 1989-92 Probes have revised applications as shown in the parts block.
PART NUMBER PART NAME CLASS
E92Z-9278-A Oil Pressure Sender (1989-92, B
2.2L Non-Turbo, MTX/ATX and
Turbo, MTX)
F02Z-9278-B Oil Pressure Sender (1990-92, B
2.2L Turbo, ATX)
F02Z-9278-A Oil Pressure Sender (1990-92, B
3.0L V-6, All Transaxles)
E92Z-9B278-A Wire Harness Assy. C
OTHER APPLICABLE ARTICLES: 90-14-9
WARRANTY STATUS: Eligible Under Basic Warranty
Coverage
OPERATION DESCRIPTION TIME
912509A Test And Replace Oil 0.5 Hr.
Pressure Switch
912509B Test And Replace Oil 1.0 Hr.
Pressure Gauge
912509C Test And Replace/Repair 0.8 Hr.
Jumper Harness
DEALER CODING
BASIC PART NO. CONDITION CODE
9B278 97
OASIS CODES: 204200