What Does P1873 Mean?
The PCM has detected that the 4WD axle lock indicator lamp circuit is shorted to battery voltage. This means the circuit is receiving unintended power, causing the lamp to illuminate continuously or erratically regardless of actual 4WD status.
Common Causes
40%
Chafed or damaged wiring harness causing short to power wire
30%
Pinched wire at connector or chassis mounting point contacting B+ source
15%
Failed transfer case control module with internal short to power
10%
Moisture intrusion in connector causing cross-circuit contamination
5%
Aftermarket accessory installation causing inadvertent power feed
Diagnostic Steps
1
Step 1: Disconnect the transfer case control module connector and check if voltage is still present on the lamp circuit wire
2
Step 2: Use a multimeter to measure voltage at the indicator lamp connector with all modules disconnected to isolate the short location
3
Step 3: Perform a visual inspection of the entire wiring harness, checking for chafing against sharp edges, hot exhaust components, or moving parts
4
Step 4: Inspect areas where harness passes through firewalls, under battery trays, and near frame rails for pinch points
5
Step 5: Check for aftermarket installations (lights, winches, radios) that may have tapped into nearby power circuits
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The PCM has detected that the 4WD axle lock indicator lamp circuit is shorted to battery voltage. This means the circuit is receiving unintended power, causing the lamp to illuminate continuously or erratically regardless of actual 4WD status.
The most common cause of P1873 (Transmission Mechanical 4-Wheel Drive Axle Lock Lamp Circuit Short To Battery) is: Chafed or damaged wiring harness causing short to power wire
Typical repair costs for P1873 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but the indicator lamp may be illuminated continuously, potentially distracting the driver. The short could drain battery if left unrepaired over extended periods.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1873 to identify the root cause.
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Quick Info
Category
Powertrain
System
4WD Transfer Case Control System
Difficulty
Type
Manufacturer
Recommended Tools
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