What Does P0859 Mean?
The traction control input signal to the PCM/TCM is reading above the expected voltage threshold. This high signal condition typically indicates a short to battery voltage in the wiring, an open ground on the circuit, or a module outputting an abnormally high signal. The PCM cannot process valid traction control requests under this condition.
Common Causes
30%
Short to battery voltage in the traction control signal wiring
25%
Open ground circuit for the traction control signal
20%
Faulty ABS/traction control module outputting high signal
15%
Disconnected or corroded connector in the circuit
10%
PCM internal fault on the traction control input
Diagnostic Steps
1
Measure the traction control input signal voltage at the PCM connector — verify it exceeds the manufacturer's maximum threshold.
2
Disconnect the traction control module and recheck the voltage — if it drops to zero, the module is the source of the high signal.
3
If voltage remains high with the module disconnected, check for a short to battery voltage in the signal wiring using a multimeter.
4
Verify the ground circuit for the traction control signal has proper continuity to chassis ground — an open ground causes the signal to float high.
5
Inspect connectors at both the traction control module and PCM for backed-out pins or corrosion that could cause an open circuit condition.
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
The traction control input signal to the PCM/TCM is reading above the expected voltage threshold. This high signal condition typically indicates a short to battery voltage in the wiring, an open ground on the circuit, or a module outputting an abnormally high signal. The PCM cannot process valid tra...
The most common cause of P0859 (Traction Control Input Signal High) is: Short to battery voltage in the traction control signal wiring
Typical repair costs for P0859 range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Traction control will be disabled due to the invalid signal. The vehicle can be driven, but without traction intervention. Exercise caution on slippery surfaces and during aggressive acceleration maneuvers.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0859 to identify the root cause.
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Quick Info
Category
Powertrain
System
Traction Control / Powertrain Integration
Difficulty
Type
Generic (SAE)
Recommended Tools
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