What does it mean?
P1177 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Electronic Throttle System Motor No. 2 Open or Shorted .
Symptoms
- Check engine light on with a reduced power or throttle warning
- Engine enters limp mode with heavily restricted throttle
- Poor or missing response from the accelerator pedal
- Rough, high or hunting idle
- Vehicle may stall when coming to a stop
- Cruise control unavailable
Likely causes
- Open or shorted winding in the second throttle motor
- Damaged harness between the module and the second throttle unit, often at a flex point or where it passes a bracket
- Water, corrosion or a spread terminal in the second throttle body connector
- Second throttle plate binding through carbon build-up or a seized shaft
- Blown fuse or open supply shared by the throttle actuator circuits
- Failed driver stage in the engine control module
- Poor engine or module ground affecting the driver reference
How to fix it
- Note every stored throttle code and read the throttle position and pedal values in live data
- Inspect the second throttle unit connector for corrosion and terminal damage; look for melted pins caused by high current
- Measure the motor winding resistance and compare it with the first motor if the vehicle has two
- Test both drive wires for continuity, and for shorts to ground and to voltage, wiggling the harness while measuring
- Verify the fuse and supply feeding the throttle circuits
- Check that the throttle plate turns freely by hand with the engine off, and clean any carbon deposits
- Replace the faulty throttle unit when the winding is proven bad, then complete the relearn procedure and road test