What does it mean?
P1173 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Throttle Actuation Potentiometer Sign.2 Signal Too High .
Symptoms
- Check engine light on, usually with a reduced power warning
- Engine goes into limp mode with limited throttle opening
- Throttle response jumps or cuts out momentarily under acceleration
- Idle speed unstable, sometimes surging
- Cruise control will not engage
- Fault can appear when driving over rough surfaces if the harness is damaged
Likely causes
- Worn or scored resistive track inside the throttle position sensor, giving jumpy or high readings
- Short to the 5 volt reference or to battery voltage on the signal 2 wire
- Open or high-resistance ground for the throttle position sensor
- Water, oil mist or corrosion inside the throttle body connector
- Chafed harness where it flexes between the body and the engine
- Carbon build-up or a binding throttle plate holding the mechanism away from its expected position
- Rarely, a failed input stage in the engine control module
How to fix it
- Graph both throttle position signals in live data while opening the throttle slowly by hand; look for a spike or dropout on track 2
- Check the 5 volt reference and the sensor ground at the throttle body connector with the ignition on
- Measure signal 2 for a short to reference voltage or to battery with the connector unplugged
- Wiggle the harness while watching live data to expose an intermittent short or open
- Inspect and clean the throttle bore and plate if carbon build-up is holding the plate open
- Repair damaged wiring, then perform the throttle body relearn or idle adaptation procedure
- Replace the throttle body assembly only if the internal potentiometer track is proven faulty