DTC 21

Code 21 - Throttle Position Sensor (TPS):

Wiring Diagram for Throttle Position Sensor (TPS):

CODE 21 - THROTTLE POSITION SENSOR (TPS) CIRCUIT (SIGNAL VOLTAGE HIGH)

Circuit Description:


The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from about .4 at idle to about 5 volts at wide open throttle.

The TPS signal is one of the most important inputs used by the Electronic Control Module (ECM) for fuel control and for most of the ECM control outputs.


NOTE: On 3.0L engines wires A & C are reversed at TPS connector.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 21 will set if

^ Engine is running

^ TPS signal voltage is greater than 2.5 volts

^ Code 33 or 34 not present at first start up

^ All conditions met for 5 seconds

With closed throttle, ignition "ON" or at idle, voltage should be 3.8L, 3.8L Turbo .40 volt +/- .05 volts; 3.0L .55 volt +/- .05 volt. If not, check adjustment. See Adjustment Procedures.

2. With the TPS sensor disconnected, the TPS voltage should go low if the ECM and wiring is OK.

3. Probing CKT 452 with a test light checks the sensor ground circuit, a faulty sensor ground circuit will cause a Code 21.

Diagnostic Aids:

A "Scan" tool reads throttle position in volts. With closed throttle, ignition "ON" or at idle, voltage should be 3.8L, 3.8L Turbo .40 volt +/- .05 volt; 3.0L .55 volt +/- .05 volt.

Also some "Scan" tools will read throttle angle 0% = closed throttle 100% = WOT.

An open in CKT 452 will result in a Code 21. Refer to "Intermittents" in Diagnosis By Symptoms - No Trouble Codes Stored.


Check For:


^ Poor Connection or Damaged Harness - Inspect ECM harness connectors for backed out terminals "C13" or "D12", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.


^ Intermittent Test - If connections and harness checks out OK, monitor TPS voltage display while moving related connectors and wiring harness. If the failure is induced, the "Coolant Temperature" display will change. This may help to isolate the location of the malfunction.


^ TPS Scaling - Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition "ON". Display should vary from closed throttle TPS voltage when throttle was closed, to over (4.5 volts) 4500 mV when throttle is held at wide open throttle (WOT) position.