For 1990-2009 cars

### Diagnostic Aids

Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Are all of the stop lamps inoperative? | Go to Step 3 | Go to Step 5
3 |

1. Turn OFF the ignition.
2. Disconnect the stop lamp relay. Refer to Relay Replacement .
3. Connect a test lamp between the stop lamp switch signal circuit at the coil side of the stop lamp relay and ground.
4. Turn ON the ignition, with the engine OFF.
5. Press and release the brake pedal.

Does the test lamp illuminate?

Go to Step 4

Go to Step 9

4 |

1. Turn OFF the ignition.
2. Connect a 10-amp fused jumper between the stop lamp relay switch side supply voltage and the stop lamp voltage supply circuit at the switch side of the stop lamp relay.
3. Turn ON the ignition, with the engine OFF.

Do the stop lamps illuminate?

Go to Step 8

Go to Step 5

5 | Test the voltage supply circuit of the inoperative stop lamp for the following:

• | An open

• | A high resistance

• | A short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 6

6 | Test the ground circuit of the inoperative stop lamp for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 7
7 | Inspect for poor connections at the harness connector of the inoperative stop lamp or center high mounted stop lamp (CHMSL). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 13
8 | Inspect for poor connections at the stop lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 12
9 | Test the stop lamp switch signal circuit for the following:

• | An open

• | A high resistance

• | A short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 10

10 | Inspect for poor connections at the harness connector of the IPM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 11
11 | Replace the IPM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | --
12 | Replace the stop lamp relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 14 | --
13 | Replace the inoperable stop lamp. Refer to High Mount Stop Lamp Replacement . Did you complete the replacement? | Go to Step 14 | --
14 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2