Pinpoint Test Q: An Individual Fog Lamp Is Inoperative

Fog Lamps

Pinpoint Tests

Pinpoint Test Q: An Individual Fog Lamp Is Inoperative

Refer to Wiring Diagram Set 86, Fog Lamps for schematic and connector information. Diagrams By Number

Normal Operation

When the fog lamp relay is energized, voltage is routed through circuits 1721 (LB/BK) and 1776 (TN/OG) to the LH and RH fog lamps. The fog lamps are provided ground through circuit 1205 (BK).

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- BEC



PINPOINT TEST Q: AN INDIVIDUAL FOG LAMP IS INOPERATIVE

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: Make sure the fog lamp bulb is good before continuing diagnostics.

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.

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Q1 CHECK CIRCUIT 1205 (BK) FOR AN OPEN


- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: Inoperative Fog Lamp.
- Disconnect: BEC C1035c.
- For 4.0L or 4.6L, measure the resistance between the LH fog lamp C152-2, circuit 1205 (BK), harness side and the BEC C1035c-E10, circuit 1205 (BK), harness side; or between the RH fog lamp C162-2, circuit 1205 (BK), harness side and the BEC C1035c-C11, circuit 1205 (BK), harness side.




- For 5.4L, measure the resistance between the LH fog lamp C1322-B, circuit 1205 (BK), harness side and the BEC C1035c-E10, circuit 1205 (BK), harness side; or between the RH fog lamp C1323-B, circuit 1205 (BK), harness side and the BEC C1035c-C11, circuit 1205 (BK), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to Q2.

No
REPAIR the circuit. TEST the system for normal operation.

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Q2 CHECK CIRCUIT 1776 (TN/OG) OR CIRCUIT 1721 (LB/BK) FOR AN OPEN


- For 4.0L or 4.6L, measure the resistance between the LH fog lamp C152-1, circuit 1721 (LB/BK), harness side and the BEC C1035c-B5, circuit 1721 (LB/BK), harness side; or between the RH fog lamp C162-1, circuit 1776 (TN/OG), harness side and the BEC C1035c-E7, circuit 1776 (TN/OG), harness side.




- For 5.4L, measure the resistance between the LH fog lamp C1322-A, circuit 1721 (LB/BK), harness side and the BEC C1035c-B5, circuit 1721 (LB/BK), harness side; or between the RH fog lamp C1323-A, circuit 1776 (TN/OG), harness side and the BEC C1035c-E7, circuit 1776 (TN/OG), harness side.




- Is the resistance less than 5 ohms?

Yes
INSTALL a new BEC. TEST the system for normal operation.

No
REPAIR the circuit in question. TEST the system for normal operation.

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