John Deere CAB523629 – CAB: Hazard Lighting System Diagnosis

The Cab Control Unit (CAB) has detected a malfunction within the hazard lighting system, specifically that the left amber lights are ON when commanded OFF by the control unit. Depending on the specific Fault Mode Identifier (FMI), this indicates a short to a power source, an open circuit, or a failed component in the left amber light circuit.

• 9570 STS Combine
• 9670 STS Combine
• 9770 STS Combine
• 9870 STS Combine

1. 1

   Carefully inspect the left-hand amber warning light for any visible damage, such as cracks, moisture intrusion, or loose connections

2. 2

   Verify the hazard light switch is functioning correctly and not stuck in the 'on' position

3. 3

   Access the diagnostic trouble codes on the machine's display to see if other related codes are present to help narrow down the source

1. 1

   Isolate the fault

   Turn the key switch and all lighting systems off. If the left amber light remains illuminated, it confirms a short circuit to a power source.

2. 2

   Inspect wiring harness

   Examine the wiring harness leading to the left amber light assembly. Look for any signs of chafing, pinching, or damage that could cause a short circuit to another wire or the machine's frame.

3. 3

   Disconnect the light

   Disconnect the electrical connector at the left amber light assembly. If the light goes out, the fault is likely within the light assembly itself. If the light stays on, the short circuit is further up the harness.

4. 4

   Test the circuit

   Using a multimeter, check for voltage at the disconnected harness connector with the hazard lights commanded OFF. If voltage is present, it confirms a short in the wiring between the CAB control unit and the light; repair or replace the harness. If no voltage is present, the issue is likely a faulty light assembly or an internal short within the CAB control unit.

5. 5

   Test the light assembly

   Apply a known good 12V power source and ground to the amber light assembly. If it illuminates, the light itself is likely not the problem.

6. 6

   Inspect the CAB Control Unit

   If the wiring and light assembly are confirmed to be good, inspect the controller's connectors for any signs of corrosion or damage. A faulty driver circuit within the controller could be sending continuous power to the light, requiring replacement of the CAB unit.