Diagnostic Procedure

WARNING: This page is about a different car, the 2004 Dodge Pickup and 2004 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

Check for any related TSBs.
Ignition on, engine not running.

With the DRBIII® in Inputs/Outputs, read the Brake Switch state.

While observing the DRBIII® display, press and release the brake pedal several times.

Does the DRBIII® display Brake Switch PRESSED and RELEASED?
1. Yes --> The Brake Lamp Switch is operating properly at this time.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
2. No --> Go To 2
Turn the ignition off.
Disconnect the Brake Lamp Switch harness connector.

Using a 12-volt test light connected to ground, probe the (A108) Fused B+ circuit at the Brake Lamp Switch harness connector.

Does the test light illuminate brightly?
1. Yes --> Go To 3
2. No --> Repair the open/high resistance in the (A108) Fused B+ circuit. Check and replace fuses as necessary.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
Using a 12-volt test light connect to 12-volts, probe the Brake Lamp Switch ground circuit.
Does the test light illuminate brightly?
1. Yes --> Go To 4
2. No --> Repair the open in the (Z241) Brake Lamp Switch Ground circuit.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
Measure the resistance across the Brake Lamp Switch Signal terminal and the Ground terminal (measurement taken across the switch).
Apply and release the Brake Pedal while monitoring the ohmmeter.

Does the resistance change from below 5.0 ohms to open circuit?
1. Yes --> Go To 5
2. No --> Replace the Brake Lamp Switch.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
Disconnect the PCM harness connectors.
Measure the resistance of the (K29) Brake Lamp Switch Signal circuit.

Is the resistance below 5.0 ohms?
1. Yes --> Go To 6
2. No --> Repair the open in the (K29) Brake Lamp Switch Signal circuit.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
Disconnect the CAB harness connector.
Measure the resistance between ground and the (K29) Brake Lamp Switch Signal circuit.

Is the resistance below 100 ohms?
1. Yes --> Repair the short to ground in the (K29) Brake Lamp Switch Signal circuit.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
2. No --> Go To 7
Connect the PCM harness connectors.
Connect the CAB harness connector.

Connect the Brake Lamp Switch harness connector.

Brake pedal must be depressed in the next step.

Ignition on, engine not running.

Using a 12-volt test light connected to ground, probe the (K29) Brake Lamp Switch Signal circuit at the Brake Lamp Switch harness connector.

Is the test light illuminated and bright?
1. Yes --> Go To 8
2. No --> Replace or adjust the brake switch.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .
Turn the ignition off.
Disconnect the Brake Switch harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Ignition on, engine not running.

With the DRBIII®, actuate the S/C Vacuum Solenoid.

Using a 12-volt test light, probe the (V32) S/C Power Supply circuit in the Brake Lamp Switch harness connector.

Did the test light illuminate brightly?
1. Yes --> Go To 9
2. No --> Repair the excesssive resistance in the (V32) S/C Power Supply circuit.
  Perform POWERTRAIN VERIFICATION TEST VER - 4 .

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
If there are no possible causes remaining, view repair.
1. Repair
  1. Replace and program the Powertrain Control Module per Service Information.
  2. Perform POWERTRAIN VERIFICATION TEST VER - 4 .