P0121-THROTTLE POSITION SENSOR 1 PERFORMANCE

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the ignition on and battery voltage greater than 10.4 volts.
Set Condition:
The PCM detects that the Throttle Position Sensor 1 circuit input voltage is implausible.

Possible Causes

INTERMITTENT DTC

(F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

(K22) TP SIGNAL 1 CIRCUIT SHORTED TO VOLTAGE

(F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND

(K22) TP SIGNAL 1 CIRCUIT SHORTED TO GROUND

(F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO THE (K22) TP SIGNAL 1 CIRCUIT

(F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO THE (K922) TP SENSOR GROUND CIRCUIT

(K22) TP SIGNAL 1 CIRCUIT SHORTED TO THE (K922) TP SENSOR GROUND CIRCUIT

(F855) 5 VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE

(K22) TP SIGNAL 1 CIRCUIT OPEN OR HIGH RESISTANCE

(K922) TP SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE

THROTTLE BODY

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Diagnostic Test

1. DTC IS ACTIVE

Start the engine and allow it to reach normal operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2. (F855) 5 VOLT SUPPLY CIRCUIT VOLTAGE

Turn the ignition off.
Disconnect the Throttle Body connector.
Turn the ignition on.
Measure the voltage of the (F855) 5 Volt Supply circuit in the Throttle Body harness connector.

Is the voltage between 4.5 and 5.5 volts?

Yes

Go to 3

Go to 7

3. (K22) TP SIGNAL 1 CIRCUIT VOLTAGE

Measure the voltage of the (K22) TP Signal 1 circuit in the Throttle Body harness connector.

Is the voltage between 4.5 and 5.5 volts?

Yes

Go to 4

Go to 11

4. (K922) TP SENSOR GROUND CIRCUIT TEST

Turn the ignition off.
Using a 12 volt test light connected to 12 volts, check the (K922) TP Sensor Ground in the Throttle Body harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

Go to 5

Go to 15

5. (F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO THE (K22) TP SIGNAL 1 CIRCUIT

Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connector.
Measure the resistance between the (F855) 5 Volt Supply circuit and the (K22) TP Signal 1 circuit in the Throttle Body harness connector.

Is the resistance above 100 ohms?

Yes

Go to 6

Repair the (F855) 5 Volt Supply circuit for a short to the (K22) TP Signal 1 circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

6. THROTTLE BODY

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Throttle Body and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Inspect the Throttle Body for any condition that would result in an incorrect signal, such as damage or contamination.

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace the Throttle Body.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

7. (F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
Measure the voltage of the (F855) 5 Volt Supply circuit in the Throttle Body harness connector.

Is there any voltage present?

Yes

Repair the (F855) 5 Volt Supply circuit for a short to voltage.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 8

8. (F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Measure the resistance between ground and the (F855) 5 Volt Supply circuit in the Throttle Body harness connector.

Is the resistance above 100 ohms?

Yes

Go to 9

Repair the (F855) 5 Volt Supply circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

9. (F855) 5 VOLT SUPPLY CIRCUIT SHORTED TO THE (K922) TP SENSOR GROUND CIRCUIT

Measure the resistance between the (F855) 5 Volt Supply circuit and the (K922) TP Sensor Ground circuit in the Throttle Body harness connector.

Is the resistance above 100 ohms?

Yes

Go to 10

Repair the (F855) 5 Volt Supply circuit for a short to the (K922) TP Sensor Ground circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

10. (F855) 5 VOLT SUPPLY CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (F855) 5 Volt Supply circuit between the Throttle Body harness connector and the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes

Go to 16

Repair the (F855) 5 Volt Supply circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

11. (K22) TP SIGNAL 1 CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
Measure the voltage of the (K22) TP Signal 1 circuit in the Throttle Body harness connector.

Is there any voltage present?

Yes

Repair the (K22) TP Signal 1 circuit for a short to voltage.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 12

12. (K22) TP SIGNAL 1 CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Measure the resistance between ground and the (K22) TP Signal 1 circuit in the Throttle Body harness connector.

Is the resistance above 100 ohms?

Yes

Go to 13

Repair the (K22) TP Signal 1 circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

13. (K22) TP SIGNAL 1 CIRCUIT SHORTED TO (K922) TP SENSOR GROUND CIRCUIT

Measure the resistance between the (K22) TP Signal 1 circuit and the (K922) TP Sensor Ground circuit in the Throttle Body harness connector.

Is the resistance above 100 ohms?

Yes

Go to 14

Repair the (K22) TP Signal 1 circuit for a short to the (K922) TP Sensor Ground circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

14. (K22) TP SIGNAL 1 CIRCUIT OPEN OR HIGH RESISTANCE

Measure the resistance of the (K22) TP Signal 1 circuit between the Throttle Body harness connector and the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes

Go to 16

Repair the (K22) TP Signal 1 circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

15. (K922) TP SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE

Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) connector.
Measure the resistance of the (K922) TP Sensor Ground circuit between the Throttle Body harness connector and the Powertrain Control Module (PCM) harness connector.

Is the resistance below 5.0 ohms?

Yes

Go to 16

Repair the circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

16. POWERTRAIN CONTROL MODULE (PCM)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Throttle Body and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).