P0859 code meaning
Traction Control Input Signal High
What P0859 means
The traction control input carries the request of the ABS/stability module to the engine module to cut torque when wheels spin. Older cars used a wire with a voltage or duty-cycle signal, hence the low and high variants; today it is a CAN message, where pure loss of communication sets U0121 or U0415 instead. California's OBD rule counts traction control as a safety-only system that may be exempted, so these codes normally carry no MIL. P0859 means a wired signal stays above its upper limit: short to battery or 5 V, or an open line with a pull-up in the receiver. No maker documents the code; the request is discarded and traction control switched off.
P0859 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0859
- Traction or stability control lamp on, system switched off
- No torque reduction when wheels spin
Common causes of P0859
- Most likelySignal wire shorted to voltage
- PossibleOpen circuit with pull-up in the engine module
- PossibleGround fault of the brake module
- Less likelyModule faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ABS control moduleEngine control moduleSerial data lineSensor wiring
What each part of P0859 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 8 | Area: transmission. |
| 59 | The exact fault in that area. |
What to do next
- Note P0859 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0859
What does P0859 mean?
P0859 means "Traction Control Input Signal High". The traction control input carries the request of the ABS/stability module to the engine module to cut torque when wheels spin. It is a generic code, so it means the same on every make.
Is it safe to drive with P0859?
P0859 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0859 fail an emissions test?
P0859 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0859 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P0859 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.