What Does C1860 Mean?
The PRNDL input circuit #3 has an electrical failure, indicating a problem with the third digital input from the transmission range sensor or gear selector switch. The control module uses a combination of input states to decode the selected gear position. With this input failed, certain gear positions may be unreadable. The driver may see an incorrect gear display, experience no-start conditions in Park, or have the transmission locked in a single gear.
Common Causes
35%
Worn or failed transmission range sensor contacts on the #3 circuit, often from age and thermal cycling of the ATF
25%
Open or high-resistance wiring on the PRNDL #3 circuit between the sensor and the control module
20%
Connector corrosion or pin damage at the transmission range sensor, especially if ATF has leaked into the connector body
12%
Shift cable or linkage misadjustment preventing proper engagement of the range sensor detents
8%
Control module input driver failure on the #3 circuit preventing proper signal detection
Diagnostic Steps
1
Using the scan tool, monitor all four PRNDL inputs simultaneously while cycling the gear selector through P-R-N-D-L. Note whether input #3 ever toggles state, and compare the overall binary pattern to the manufacturer's truth table.
2
Inspect the transmission range sensor and its connector for signs of ATF leakage, corrosion, or heat damage. ATF wicking into the connector is a very common cause of circuit failures.
3
Perform a continuity and voltage check on the PRNDL #3 wire from the TRS connector to the module connector. The wire should show less than 2 ohms resistance and no shorts to ground or power.
4
Check the shift cable adjustment by verifying the manual lever detent positions mechanically align with the selector positions. Adjust the cable or linkage as needed.
5
If the range sensor is externally mounted, remove it and inspect the internal contacts for wear, pitting, or carbon tracking. Replace if any contact surface is compromised.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The PRNDL input circuit #3 has an electrical failure, indicating a problem with the third digital input from the transmission range sensor or gear selector switch. The control module uses a combination of input states to decode the selected gear position. With this input failed, certain gear positio...
The most common cause of C1860 (PRNDL Input #3 Circuit Failure) is: Worn or failed transmission range sensor contacts on the #3 circuit, often from age and thermal cycling of the ATF
Typical repair costs for C1860 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
With PRNDL input #3 failed, the vehicle may not correctly identify all gear positions, potentially causing unexpected gear engagement or failure to start if the Park position is not recognized. Backup lights and neutral safety switch functions may also be affected. Drive cautiously to a repair facility but avoid prolonged driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1860 to identify the root cause.
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Quick Info
Category
Chassis
System
Transmission / Gear Selection
Difficulty
Type
Manufacturer
Recommended Tools
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