Engine
P0122 - Throttle Position Sensor 1 Circuit Low, 4.0L
For wiring diagrams, refer to.
• When Monitored: With the engine running and battery voltage greater than 10 volts.
• Set Condition: The PCM detects that the sensor input voltage is less than the minimum acceptable value.
• Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - DTC is Active
• 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.
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.
• 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 Test Step 2 => [ Test
Step 2 - 5 Volt Supply Circuit Voltage ]
No
• Refer to the checking for an intermittent DTC diagnostic procedure. Refer to => Non-DTC Based Diagnostics. Checking for an Intermittent DTC
Test Step 2 - 5 Volt Supply Circuit Voltage
• Turn the ignition OFF.
• Disconnect the throttle body connector.
• Turn the ignition ON.
• Measure the voltage of the 5 volt supply circuit in the throttle body harness connector.
Is the voltage more than 4.5 volts?
Yes
• Go to Test Step 6 => [ Test
Step 6 - TP Signal 1 Circuit Shorted to Ground ]
No
• Go to Test Step 3 => [ Test
Step 3 - 5 Volt Supply Circuit Shorted to Ground ]
Test Step 3 - 5 Volt Supply Circuit Shorted to Ground
• Turn the ignition ON.
• Disconnect the C2 PCM harness connector.
• Measure the resistance between ground and the 5 volt supply circuit in the throttle body harness connector.
Is the resistance more than 1000 ohms?
Yes
• Go to Test Step 4 => [ Test
Step 4 - 5 Volt Supply Circuit Shorted to the TP Sensor Ground Circuit ]
No
• Repair the short to ground in the 5 volt supply circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 4 - 5 Volt Supply Circuit Shorted to the TP Sensor Ground Circuit
• Measure the resistance between the 5 volt supply circuit and the TP sensor ground circuit in the throttle body harness connector.
Is the resistance more than 100 ohms?
Yes
• Go to Test Step 5 => [ Test
Step 5 - 5 Volt Supply Circuit Open or High Resistance ]
No
• Repair the short between the 5 volt supply circuit and the TP sensor ground circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 5 - 5 Volt Supply Circuit Open or High Resistance
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 to perform diagnosis.
• Measure the resistance of the 5 volt Supply circuit between the throttle body harness connector and the appropriate terminal of special tool #8815.
Is the resistance less than 5.0 ohms?
Yes
• Go to Test Step 13 => [ Test
Step 13 - PCM ]
No
• Repair the open or excessive resistance in the 5 volt supply circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 6 - TP Signal 1 Circuit Shorted to Ground
• Turn the ignition OFF.
• Disconnect the C2 PCM harness connector.
• Measure the resistance between ground and the TP signal 1 circuit in the throttle body harness connector.
Is the resistance more than 100 ohms?
Yes
• Go to Test Step 7 => [ Test
Step 7 - TP Signal 1 Circuit Shorted to TP Sensor Ground Circuit ]
No
• Repair the short to ground in the TP signal 1 circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 7 - TP Signal 1 Circuit Shorted to TP Sensor Ground Circuit
• Measure the resistance between the TP signal 1 circuit and the TP sensor ground circuit in the throttle body harness connector.
Is the resistance more than 100 ohms?
Yes
• Go to Test Step 8 => [ Test
Step 8 - TP Signal 1 Circuit Shorted to ETC Motor (+) Circuit ]
No
• Repair the short between the TP signal 1 circuit and the TP sensor ground circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 8 - TP Signal 1 Circuit Shorted to ETC Motor (+) Circuit
• Measure the resistance between the TP signal 1 circuit and the ETC motor (+) in the throttle body harness connector.
Is the resistance less than 100 ohms?
Yes
• Repair the short between the ETC motor (+) circuit and the TP signal 1 circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
No
• Go to Test Step 9 => [ Test
Step 9 - TP Signal 1 Circuit Shorted to ETC Motor (-) Circuit ]
Test Step 9 - TP Signal 1 Circuit Shorted to ETC Motor (-) Circuit
• Measure the resistance between the TP signal 1 circuit and the ETC motor (-) in the throttle body harness connector.
Is the resistance less than 100 ohms?
Yes
• Repair the short between the TP signal 1 circuit and the ETC motor (-) circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
No
• Go to Test Step 10 => [ Test
Step 10 - Excessive Resistance in TP Signal 1 Circuit ]
Test Step 10 - Excessive Resistance in TP Signal 1 Circuit
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 to perform diagnosis.
• Measure the resistance of the TP signal 1 circuit between the throttle body harness connector and the appropriate terminal of special tool #8815.
Is the resistance less than 5.0 ohms?
Yes
• Go to Test Step 11 => [ Test
Step 11 - Throttle Position Sensor 1 Voltage ]
No
• Repair the excessive resistance in the TP signal 1 circuit.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 11 - Throttle Position Sensor 1 Voltage
• Turn the ignition OFF.
• Connect the C2 PCM harness connector.
• Turn the ignition ON.
• With the scan tool, read the throttle position sensor 1 voltage.
• The sensor voltage should be approximately 5.0 volts (plus or minus 0.1 volt) with the throttle body connector disconnected.
• Turn the ignition OFF.
• Connect a jumper wire between the TP signal 1 circuit and the TP sensor ground circuit in the throttle body harness connector.
• Turn the ignition ON.
• With a scan tool, read the throttle position sensor 1 voltage.
• The sensor voltage should be approximately 0.0 volts (plus or minus 0.1 volt) with the jumper wire in place.
Does the scan tool display the voltage as described more than?
Yes
• Go to Test Step 12 => [ Test
Step 12 - Throttle Body ]
No
• Go to Test Step 13 => [ Test
Step 13 - PCM ]
Test Step 12 - Throttle Body
• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the throttle body and the PCM.
• Look for any chafed, pierced, pinched, or partially broken wires.
• Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
• 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. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
No
• Replace the throttle body.Disconnect the battery prior to replacing the throttle body. With the scan tool, perform the ETC relearn function after replacement.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 13 - PCM
• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the throttle body and the PCM.
• Look for any chafed, pierced, pinched, or partially broken wires.
• Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
• 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. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
No
• Replace and program the PCM.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test