What Does C1855 Mean?
The accelerator position sensor signals are conflicting, meaning the two or more sensor tracks within the accelerator pedal assembly are reporting different throttle positions. This is a critical safety concern as the vehicle control module cannot determine the driver's true throttle intent. The driver may experience erratic throttle response, limp mode, or a completely unresponsive accelerator pedal.
Safety Warning
This is a critical safety fault. The vehicle will likely enter a failsafe/limp mode with severely reduced power. Do not continue driving until the conflict is resolved, as the system may interpret incorrect throttle commands. In worst cases, the vehicle may shut down throttle response entirely. Immediate diagnosis is required.
Common Causes
40%
Worn or failing accelerator pedal position sensor with internal track wear causing signal divergence between redundant circuits
25%
Corroded or damaged connector at the accelerator pedal assembly causing intermittent signal on one circuit
20%
Wiring harness damage between the APP sensor and the control module, such as chafing or rodent damage
10%
5V reference voltage issue from the control module affecting one sensor track more than the other
5%
Floor mat or mechanical obstruction partially binding the accelerator pedal causing erratic sensor readings
Diagnostic Steps
1
Monitor both APP sensor voltage signals (APP1 and APP2) simultaneously while slowly sweeping the pedal from idle to wide-open-throttle. APP1 should increase from ~0.5V to ~4.5V and APP2 should mirror proportionally (often ~0.25V to ~2.25V). Any deviation, dead spots, or erratic jumps indicate a fault.
2
Inspect the accelerator pedal assembly connector for corrosion, water intrusion, and bent or backed-out pins. Verify the connector lock is fully seated.
3
With the pedal unplugged, measure the 5V reference and signal ground at the module-side connector. Both reference circuits should read 4.95-5.05V with key-on-engine-off.
4
Perform a wiggle test on the APP sensor wiring harness from the pedal to the module while monitoring live data. Pay attention to areas near the steering column and firewall pass-through.
5
Verify no floor mats, cargo, or debris are interfering with full pedal travel. Check pedal pivot and return spring for smooth, unrestricted operation.
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The accelerator position sensor signals are conflicting, meaning the two or more sensor tracks within the accelerator pedal assembly are reporting different throttle positions. This is a critical safety concern as the vehicle control module cannot determine the driver's true throttle intent. The dri...
The most common cause of C1855 (Acceleration Position Sensor Conflict) is: Worn or failing accelerator pedal position sensor with internal track wear causing signal divergence between redundant circuits
Typical repair costs for C1855 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This is a critical safety fault. The vehicle will likely enter a failsafe/limp mode with severely reduced power. Do not continue driving until the conflict is resolved, as the system may interpret incorrect throttle commands. In worst cases, the vehicle may shut down throttle response entirely. Immediate diagnosis is required.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1855 to identify the root cause.
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Quick Info
Category
Chassis
System
Electronic Throttle Control
Difficulty
Type
Manufacturer
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