Section 13-09A: Gauges, Warning Devices—Low Oil Level Indication System
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

  

PINPOINT TEST A: LOW OIL LEVEL INDICATOR STAYS ON AFTER STARTING ENGINE — OIL NOT LOW

 

A1 CHECK OIL LEVEL SENSOR AND CIRCUIT FOR SHORT TO GROUND 

Yes
GO to A2 .

No
GO to A3 .

 

A2 CHECK LOW OIL LEVEL SENSOR RESISTANCE

Yes
REPLACE low oil level sensor . RESTORE vehicle. RETEST system.

No
GO to A3 .

 

A3 CHECK LOW OIL LEVEL CIRCUIT

  • Using ohmmeter connected to a known good ground, connect second lead to Circuit 258 (W/PK) at sensor connector.
  • Measure resistance.
  • Is resistance less than 8K ohms?
Yes
SERVICE Circuit 258 (W/PK) for short to ground. RESTORE system. RETEST vehicle.

No
REPLACE low oil level relay . RESTORE vehicle. RETEST system.

  

PINPOINT TEST B: LOW OIL LEVEL INDICATOR DOES NOT STAY ON WHEN OIL IS LOW

 

B1 CHECK OIL LEVEL SENSOR AND CIRCUIT FOR OPEN CIRCUIT 

  • Ensure engine has been off for five minutes.
  • Ensure oil is at least 1.4L (1.5 Qt) low.
  • Disconnect low oil level sensor at oil pan .
  • Using a jumper wire, connect one end to a known good ground. Connect other end to Circuit 258 (W/PK) at sensor connector.
  • Start engine, observe indicator at instrument panel .
  • Did indicator illuminate?
Yes
REPLACE low oil level sensor . RESTORE vehicle. RETEST system.

No
GO to B2 .

 

B2 CHECK LOW OIL LEVEL CIRCUIT

  • Leave jumper wire connected to ground and sensor connector.
  • Gain access to low oil level relay at instrument panel .
  • Using an ohmmeter connected to a known good ground, connect second lead to Pin 2, Circuit 258 (W/PK) at relay connector.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to B3 .

No
SERVICE Circuit 258 (W/PK) for open circuit. RESTORE vehicle. RETEST system.

 

B3 CHECK LOW OIL WARNING RELAY GROUND

  • Remove ohmmeter lead from Pin 2 and connect it to Pin 1, Circuit 57 (BK).
  • Read resistance.
  • Is resistance 5 ohms or less?
Yes
GO to B4 .

No
SERVICE open in Circuit 57 (BK). RESTORE vehicle. RETEST system.

 

B4 CHECK WARNING RELAY SUPPLY

  • Using a test lamp connected to a known good ground, connect test lamp probe to Pin 5, Circuit 640 (R/Y).
  • Did test lamp illuminate?
Yes
GO to B6 .

No
GO to B5 .

 

B5 CHECK RELAY SUPPLY CIRCUIT

  • Using test lamp, check for power at fuse 15 (10A) output side.
  • Did test lamp illuminate?
Yes
SERVICE Circuit 640 (R/Y) for an open. RESTORE vehicle. RETEST system.

No
REPLACE fuse 15 (10A). RESTORE vehicle. RETEST system.

 

B6 CHECK RELAY SIGNAL TO INSTRUMENT PANEL

  • Reconnect low oil level relay and sensor.
  • Using ohmmeter connected to known good ground, check continuity at Pin 7, Circuit 208 (GY).
  • Is resistance 5 ohms or less?
Yes
GO to B7 .

No
SERVICE Circuit 208 (GY) for open circuit. RESTORE vehicle. RETEST system.

 

B7 CHECK POWER SUPPLY

  • Using a test lamp, check for power at Pin 8, Circuit 640 (R/Y).
  • Did test lamp illuminate?
Yes
GO to B8.

No
SERVICE Circuit 640 (R/Y) for an open. RESTORE vehicle. RETEST system.

 

B8 CHECK LOW OIL INDICATOR BULB

  • Remove indicator bulb.
  • Carefully inspect bulb.
  • Is bulb damaged?
Yes
REPLACE bulb. RESTORE vehicle. RETEST system.

No
REPLACE instrument cluster . RESTORE vehicle. RETEST system.

  

PINPOINT TEST C: LOW OIL LEVEL INDICATOR BLINKS INTERMITTENTLY WHILE DRIVING

 

C1 CHECK CIRCUITRY ROUTING AND CONNECTIONS 

  • Check for loose connections at all connectors.
  • Ensure indicator bulb is installed properly and tight.
  • Are all connections clean and tight?
Yes
REPLACE low oil level relay . RESTORE vehicle. RETEST system.

No
SERVICE connectors or bulb. RESTORE vehicle. RETEST system.