Possible causes

– Faulty electric throttle control actuator (TP sensor 1 and 2)
– Throttle Position Sensor harness is open or shorted
– Throttle Position Sensor circuit poor connection
– Faulty accelerator pedal position sensor

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P2135 GMC Description

The throttle Position (TP) sensors 1 and 2 are potentiometer type sensors each with 3 circuits.

– A 5 – volt reference circuit.
– A low reference circuit.
– A signal circuit

The TP sensor are used to determine the throttle plate angle for various engine management systems. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module whit signal voltage proportional to the throttle plate movement. Both TP sensor signal voltage are low at close throttle and increase as the throttle opens. When the control module detects that the TP sensor 1 signal and TP sensor 2 signals disagree or the signal voltages are outside the predetermined range, the P2135 code is set.

GMC Technical Service Bulletins for P2135 code