Code 21 - TPS Circuit High
Code 21 indicates the ECM has seen a high TPS voltage for more than 10 seconds, below a specified RPM (normally curb idle) or below a specified engine load. Due to the pull-up resistor between terminals "21" and "2" within the ECM, an open in the TPS circuit will place about 5 volts (high TPS signal) at terminal "2" of ECM.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- This test checks the circuits from the TPS connector back to the ECM. Installing a jumper lead between harness terminals "B" and "C" should lower voltage at ECM terminal "2" below 2.5 volts.
- A high voltage of 2.5 volts or more at this point would indicate circuit 417 is open or shorted to circuit 416, or circuit 452 is open. If both circuits check okay, problem is faulty ECM.
- A low voltage reading of less than 2.5 volts indicates the TPS or its connections are faulty.