What Does P1900 Mean?
The engine coolant level warning lamp circuit has a short to ground condition. This causes the lamp to illuminate incorrectly or not function properly for low coolant warnings.
Common Causes
35%
Damaged wiring harness with exposed wire touching ground
30%
Failed instrument cluster or internal cluster circuit fault
20%
Shorted bulb socket or LED driver circuit in cluster
15%
PCM internal driver circuit failure
Diagnostic Steps
1
Step 1: Disconnect instrument cluster connector and check if short to ground clears using ohmmeter
2
Step 2: Inspect wiring harness from PCM to instrument cluster for damaged insulation or pinch points
3
Step 3: Test PCM lamp driver output circuit resistance to ground with cluster disconnected
4
Step 4: Check for aftermarket accessories or modifications that may have damaged wiring
5
Step 5: Verify proper operation of coolant level lamp bulb/LED by commanding lamp on with scan tool
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The engine coolant level warning lamp circuit has a short to ground condition. This causes the lamp to illuminate incorrectly or not function properly for low coolant warnings.
The most common cause of P1900 (Engine Coolant Level Lamp Circuit Short to Ground) is: Damaged wiring harness with exposed wire touching ground
Typical repair costs for P1900 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of low coolant warning lamp may prevent driver awareness of cooling system problems. Monitor coolant level manually until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1900 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Warning Lamp Circuit
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
