DTC 21

DTC 21 - Throttle Position (TP) Sensor Circuit (Signal Voltage High):

TPS Sensor, ECT Sensor, IAT Sensor Wiring Circuit:

Circuit Description:

The Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from about .4 at idle to above 4 volts at Wide Open Throttle (WOT).

The TP sensor signal is one of the most important inputs used by the PCM for fuel control and for most of the PCM control outputs. DTC 21 will set if:
^ TP sensor voltage is greater than 4.8 volts at any time.
OR
^ Engine is running and air flow is less than 15 gm/sec.
^ TP sensor signal voltage is greater than 1.06 volt.
^ DTC 34 not present.
^ All conditions met for 5 seconds.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. With closed throttle, ignition "ON," or at idle, voltage at "BB10" should be .20-.74 volt.
2. With the TP sensor disconnected, the TP sensor voltage should go low and a DTC 22 will set. This test verifies that the PCM and wiring are OK.
3. Probing CKT 452 with a test light checks the sensor ground circuit. A faulty sensor ground circuit will cause a DTC 21.

NOTICE: If a DTC 21 is set, the PCM will not allow 4th gear, cruise control, or TCC operation.

Diagnostic Aids:

The Tech 1 displays throttle position in volts. With closed throttle, ignition "ON" or at idle, voltage should be .20-. 74 volt. If not, replace sensor.

An open in CKT 452 may result in DTCs 15 and 21. - Intermittent Malfunctions

Check for:
^ Poor Connection or Damaged Harness - Inspect PCM harness connectors for backed out terminal "BB10", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Intermittent Test - Monitor TP sensor voltage on Tech 1 while moving related connectors and wiring harness. If the failure is induced, the display will change. This may help to isolate the location of the malfunction.
^ TP Sensor Scaling - Observe TP sensor voltage display on Tech 1 while slowly depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from closed throttle TP sensor voltage (.20-.74 volt) to over 4.0 volts when throttle is held at Wide Open Throttle (WOT) position. Typically, accelerator pedal travel only yields 4.1 or 4.2 volts maximum. If a TP sensor voltage of over 4.8 volts is observed at any point in normal accelerator pedal travel, replace TP sensor.