P1873: 4WD Indicator Lamp Circuit Malfunction
The P1873 code indicates that the Powertrain Control Module (PCM) or Transfer Case Control Module (TCM) has detected a fault in the electrical circuit for the 4WD indicator lamp on the instrument cluster. This means the module cannot properly control the lamp's on/off state due to an open circuit, short to ground, or short to voltage in the wiring that powers or controls the indicator.
01. Most Common Causes
- Blown or damaged 4WD indicator bulb
- Open circuit in the wiring between the PCM/TCM and the instrument cluster
- Short to ground or battery voltage in the lamp control circuit
- Loose, corroded, or damaged connector at the instrument cluster or PCM/TCM
- Internal failure of the PCM/TCM driver that controls the lamp
- Fault in the transfer case control module (if separate)
02. Symptoms You Will Notice
- 4WD indicator light stays on or off regardless of 4WD engagement
- Inoperative 4WD indicator lamp
03. Step-by-Step Diagnosis
Check the 4WD indicator bulb and replace if burned out
Inspect wiring and connectors for damage, corrosion, or loose connections
Test for open or short circuits in the lamp control circuit using a multimeter
Verify PCM/TCM operation and check for related trouble codes
1. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive with a P1873 code, but the 4WD indicator may not function correctly, which could lead to confusion about the 4WD system status. It is recommended to diagnose and repair the issue promptly.
How much does it cost to fix?▼
The repair cost typically ranges from $100 to $400, depending on the cause. A simple bulb replacement may cost under $50, while wiring repairs or module replacement can be more expensive.