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Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0504

Step Action Yes No
Schematic Reference: Exterior Lights Schematics  and Cruise Control Schematics in Cruise Control
Connector End View Reference: Master Electrical Component List in Wiring Systems
1 Did you perform the Diagnostic System Check - Lighting Systems? Go to Step 2  Go to Diagnostic System Check - Lighting Systems 
2
IMPORTANT: The stop lamp switch must be adjusted correctly for proper operation. Refer to Stop Lamp Switch Adjustment .
  1. With the scan tool, observe the Stop Lamp Pedal Switch parameter and TCC Brake Pedal Switch parameter.
  2. Press and release the brake pedal.
Does the Stop Lamp Pedal Switch parameter and TCC Brake Pedal Switch parameter display change closely with each other?		 Go to Diagnostic Aids Go to Step 3 
3
  1. With the scan tool, observe the TCC Brake Pedal Switch parameter.
  2. Press and release the brake pedal.
Does the TCC Brake Pedal Switch parameter display change with the brake pedal position?		 Go to Step 6  Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Disconnect the stop lamp switch.
  3. Turn ON the ignition, with the engine OFF.
Does the TCC Brake Pedal Switch parameter display released?		 Go to Step 5  Go to Step 12 
5
  1. Turn OFF the ignition.
  2. Connect a 10-amp fused jumper between the ignition positive voltage circuit of the stop lamp switch and the torque converter clutch (TCC) brake switch/cruise control release signal circuit of the stop lamp switch.
  3. Turn ON the ignition, with the engine OFF.
Does the TCC Brake Pedal Switch parameter display applied?		 Go to Step 15  Go to Step 8 
6
  1. Turn OFF the ignition.
  2. Disconnect the stop lamp switch.
  3. Turn ON the ignition, with the engine off.
  4. With the scan tool, observe the Stop Lamp Pedal Switch parameter.
Does the Stop Lamp Pedal Switch parameter display Released?		 Go to Step 7  Go to Step 10 
7
  1. Turn OFF the ignition.
  2. Connect a 20-amp fused jumper between the battery positive voltage circuit of the stop lamp switch and the stop lamp switch signal circuit.
  3. Turn ON the ignition, with the engine OFF.
Does the Stop Lamp Pedal Switch parameter display Applied?		 Go to Step 15  Go to Step 11 
8 Test the ignition positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 9 
9 Test for an open or short to ground in the TCC brake switch/cruise control release signal circuit of the stop lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 14 
10 Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 14 
11 Test the battery positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 13 
12 Test the TCC brake switch/cruise control release signal circuit of the stop lamp switch for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 16 
13 Test the stop lamp switch signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 14 
14 Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 16 
15 Inspect for poor connections at the harness connector of the stop lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 17 
16
IMPORTANT: Program the replacement ECM.
Replace the ECM. Refer to Engine Control Module (ECM) Replacement in Engine Controls 3.6L (LY7).Did you complete the replacement?		 Go to Step 18  -
17 Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement .
Did you complete the replacement?		 Go to Step 18  -
18
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 Go to Step 2  System OK
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