DTC P0121 [AJ] (VIN: JM0 LW10J300 301406-, JMZ LW69J7*# 307683-, JM8 LW28J**# 301514-, JM8 LW28A**# 301514- (Assumed))

BME010200100W14

DTC P0121

Throttle position stuck close (lower than expected)/open (higher than expected)

DETECTION CONDITION

• If PCM detects that throttle valve opening angle is below 12.5% for 5 s after following conditions are met, PCM determines that TP is stuck close:
MONITORING CONDITION
- Engine coolant temperature above 70 °C {158 °F}
- MAF sensor signal above 88.3 g/s {11.7 lb/minutes}
• If PCM detects that throttle valve opening angle is above 50% for 5 s after following conditions are met, PCM determines that TP is stuck open:
MONITORING CONDITION
- Engine speed above 500 rpm
- MAF sensor signal below 8.93 g/seconds {1.18 lb/minutes}
Diagnostic support note
• This is a continuous monitor (CCM).
• The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.

POSSIBLE CAUSE

• TP sensor malfunction
• Electrical corrosion in TP signal circuit
• Voltage drops in constant voltage (Vref) supply circuit
• Voltage drops in ground circuit
• MAF sensor malfunction
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1
VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
• Has FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record FREEZE FRAME DATA on repair order, then go to the next step.
2
VERIFY RELATED PENDING CODE OR STORED DTC
• Turn the ignition switch to the ON position (Engine off).
• Retrieve pending or stored DTC using the WDS or equivalent.
• Is DTC P0101 also retrieved?
Yes
Go to DTC P0101 troubleshooting procedure.
No
Go to the next step.
3
VERIFY RELATED REPAIR INFORMATION AVAILABILITY
• Check for related Service Information and/or on-line repair information availability.
• Is any related repair information available?
Yes
Perform repair or diagnosis according to the available repair information.
• If the vehicle is not repaired, then go to the next step.
No
Go to the next step.
4
VERIFY CURRENT INPUT SIGNAL STATUS - IS CONCERN INTERMITTENT OR CONSTANT
• Start the engine.
• Access ECT, TP and MAF PIDs using the WDS or equivalent.
• Warm up the engine until ECT PID is above 70 °C {158 °F}
• Drive the vehicle.
• Read TP PID while MAF PID is above 88.3 g/s {11.7 lb/min}.
• Is TP PID reading above 12.5%?
Yes
Go to Step 7.
No
Go to the next step.
5
VERIFY TP PID
• Start engine.
• Access TP, MAF and RPM PIDs using the WDS or equivalent.
• Read TP PID while MAF PID is below 5.3g/s {0.7 lb/min} and RPM PID is above 500 rpm.
• Is TP PID reading above 50%?
Yes
Go to Step 12.
No
Go to the next step.
6
VERIFY CURRENT INPUT SIGNAL STATUS - IS CONCERN INTERMITTENT OR CONSTANT
• Drive the vehicle and read MAF PID.
• Does MAF PID change in compliance with driving condition?
Yes
Intermittent concern exists. Go to INTERMITTENT CONCERNS troubleshooting procedure.
No
Check Mass airflow sensor and related circuits and terminals.
Repair or replace as necessary, then go to Step 16.
7
CHECK TP SENSOR TERMINALS FOR ELECTRICAL CORROSION
• Turn the ignition switch off.
• Disconnect TP sensor connector
• Check for electrical corrosion on male and female TP sensor terminals.
• Is any electrical corrosion found?
Yes
Repair or replace suspected terminal or TP sensor, then go to Step 11.
No
Go to the next step.
8
VERIFY TP SENSOR
• Does TP sensor resistance smoothly change while gradually opening throttle valve?
Yes
Go to the next step.
No
Replace TP sensor, then go to Step 11.
9
CHECK PCM TERMINALS FOR ELECTRICAL CORROSION
• Disconnect PCM connector.
• Check for electrical corrosion on PCM male and female terminals.
• Is any electrical corrosion found?
Yes
Repair terminal, then go to Step 11.
No
Go to the next step.
10
CHECK CONSTANT VOLTAGE SUPPLY AND TP SIGNAL CIRCUITS FOR VOLTAGE DROP
• Connect the PCM connector.
• Turn the ignition switch to the ON position (Engine off).
• Check voltage between following terminals:
- TP sensor connector terminal C (harness-side) and PCM terminal 33
- TP sensor connector terminal B (harness-side) and PCM terminal 40
• Is voltage approx. 0 V?
Yes
Remove PCM, then go to the next step.
No
Check for rust or corrosion on PCM terminals 40 and 33 (harness-side).
• Repair or replace suspected terminal.
Remove PCM, then go to the next step.
11
VERIFY TROUBLESHOOTING OF DTC P0121 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Start the engine.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Access ECT, TP and MAF PIDs using the WDS or equivalent.
• Warm up the engine until ECT PID is reading above 70 °C {158°F}.
• Drive the vehicle and read TP and MAF PIDs.
• Verify PIDs reading are within specifications
MAF PID: above 88.3 g/s {11.7 lb/min}
TP PID: above 12.5% more than 5 s
• Is pending code of same DTC present?
Yes
Replace PCM, then go to Step 17.
No
Go to Step 17.
12
CHECK TP SENSOR TERMINALS FOR ELECTRICAL CORROSION
• Turn the ignition switch off.
• Disconnect TP sensor connector.
• Check for electrical corrosion on male and female TP sensor terminals.
• Is any electrical corrosion found?
Yes
Repair or replace suspected terminal or TP sensor, then go to Step 16.
No
Go to the next step.
13
CHECK GROUND CIRCUIT FOR VOLTAGE DROP
• Check resistance between TP sensor terminal A (harness-side) and body ground.
• Is resistance approx. 0 ohm ?
Yes
Go to the next step.
No
Repair or replace for rust or corrosion on PCM terminal 20 (harness-side)
• Repair or replace suspected terminal.
Go to Step 16.
14
VERIFY TP SENSOR
• Does resistance smoothly change while gradually opening throttle valve?
Yes
Go to the next step.
No
Replace TP sensor, then go to Step 16.
15
CHECK PCM TERMINALS FOR ELECTRICAL CORROSION
• Disconnect PCM connector.
• Check for electrical corrosion on PCM and PCM connector male and female terminals.
• Is any electrical corrosion found?
Yes
Repair terminal, then go to the next step.
No
Go to the next step.
16
VERIFY TROUBLESHOOTING OF DTC P0121 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Start engine.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Access RPM, TP and MAF PIDs using the WDS or equivalent.
• Verify TP PID is reading below 50% while MAF PID is below 8.25 g/s {1.09 lb/min} and RPM PID is above 500 rpm.
• Is pending code of same DTC present?
Yes
Replace PCM, then go to the next step.
No
Go to the next step.
17
VERIFY AFTER REPAIR PROCEDURE
• Perform the "After Repair Procedure".
• Are any DTCs present?
Yes
Go to the applicable DTC inspection.
No
Troubleshooting completed.