P0121
P0121-THROTTLE POSITION SENSOR 1 PERFORMANCE
For a complete wiring diagram refer to Diagrams/Electrical.
- When Monitored:
Ignition on and No MAP Sensor DTCs set.
- Set Condition:
The PCM detects that the sensor input voltage does not fall within a valid range based on engine speed and load. Two Trip Fault. ETC light will illuminate. P2135 should set with this code also.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
NOTE: Diagnose and repair any Throttle Body circuit, system voltage, or sensor supply voltage DTCs before continuing with this test.
Start the engine and allow it to reach 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.
NOTE: If the DTC does not reset it may be necessary to test drive the vehicle.
Is the status Active for this DTC?
Yes
- Go To 2
No
- Go To 9
2. EXCESSIVE RESISTANCE IN THE (K22) TP SENSOR NO.1 SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the C2 PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
Using a voltmeter perform a voltage drop test. Backprobe the (K22) TP Sensor No.1 Signal circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
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.
Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.
Is the voltage below 0.5 of a volt?
Yes
- Go To 3
No
- Repair the excessive resistance in the (K22) TP Sensor No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
3. EXCESSIVE RESISTANCE IN THE (K122) TP SENSOR NO.2 SIGNAL CIRCUIT
Turn the ignition off.
Move the voltmeter leads to backprobe the (K122) TP Sensor No.2 Signal circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
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.
Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.
Is the voltage below 0.5 of a volt?
Yes
- Go To 4
No
- Repair the excessive resistance in the (K122) TP Sensor No.2 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
4. EXCESSIVE RESISTANCE IN THE (K855) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Move the voltmeter leads to backprobe the (K855) 5-volt Supply circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
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.
Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.
Is the voltage below 0.5 volts?
Yes
- Go To 5
No
- Repair the excessive resistance in the (K855) 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
5. EXCESSIVE RESISTANCE IN THE (K922) SENSOR RETURN CIRCUIT
Turn the ignition off.
Move the voltmeter leads to backprobe the (K922) Sensor Return circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.
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.
Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.
Is the voltage below 0.5 volts?
Yes
- Go To 6
No
- Repair the excessive resistance in the (K922) Sensor Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO THE (K122) TP SENSOR NO.2 SIGNAL CIRCUIT
Turn the ignition off.
Remove special tool #8815 and #8815-1 leaving the C2 PCM harness connector disconnected.
Disconnect the Throttle Body harness connector.
Measure the resistance between the (K22) TP Sensor No.1 Signal circuit and the (K122) TP Sensor No.2 Signal circuit in the Throttle Body harness connector.
Is the resistance below 5.0 ohms?
Yes
- Repair the short between the (K122) TP Sensor No.2 Signal circuit and the (K22) TP Sensor No.1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 7
7. THROTTLE POSITION SENSOR
Connect the C2 PCM harness connector.
Ignition on, engine not running.
With a scan tool, monitor the TP Sensor No.1 and No.2 voltage.
Connect a jumper wire between the (K922) Sensor Return circuit and the (K22) TP Sensor No.1 Signal circuit.
NOTE: TP Sensor No.1 voltage should change from approximately 4.5 volts to less than 0.5 of a volt.
For TP Sensor No.2, connect a jumper wire between (K855) 5-volt supply circuit and the (K122) TP Sensor No.2 signal circuit.
NOTE: TP Sensor No.2 voltage should change from approximately 0 volts to 5.0 volts?
Is the voltage reading within the listed specification when the jumper wire is installed?
Yes
- Replace the Throttle Body Assembly. Disconnect the Battery when replacing the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 8
-
NOTE: Remove the jumper wire before continuing.
8. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
9. THROTTLE FOLLOWER TEST
Ignition on, engine not running.
With a scan tool, perform the Throttle Follower Test and monitor the TP Sensor No.1 or No.2 voltage.
Slowly press the throttle pedal down.
The voltage for TP Sensor No.1 should start at approximately 0.3 of a volt and increase to above 4.7 volts.
The voltage for TP Sensor No.2 should start at approximately 4.7 volts and decrease to approximately 0.3 of a volt.
Is the voltage within the range of the listed specification for the appropriate Sensor?
Yes
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
No
- Disconnect the Battery when replacing the Throttle Body Assembly. Replace the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test