DTC P0121 [L3]

BME010200100W11

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 closed:
MONITORING CONDITION
- Engine coolant temperature above 80 °C {158 °F}
- MAF sensor signal above 58.3 g/s {7.7 lb/minutes}
• If PCM detects that throttle valve opening angle is above 50% for 5 seconds after following conditions are met, the PCM determines that TP is stuck open:
MONITORING CONDITION
- Engine speed above 500 rpm
- MAF sensor signal below 4.8 g/s {0.63 lb/min.}
Diagnostic support note
• This is a continuous monitor (CCM).
• MIL illuminates if 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 PCM detects the above malfunction condition.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.

POSSIBLE CAUSE

• TP sensor malfunction
• Electrical corrosion in TP signal circuit
• Voltage drop in constant voltage supply circuit
• Voltage drop 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 next step.
No
Record FREEZE FRAME DATA on repair order, then go to next step.
2
VERIFY RELATED PENDING CODE OR STORED DTC
• Turn ignition key to ON (Engine OFF).
• Retrieve pending or stored DTC using WDS or equivalent.
• Is DTC P0101 also retrieved?
Yes
Go to DTC P0101 troubleshooting procedure.
No
Go to next step.
3
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
• Check for related Service Information availability.
• Is any related Service Information available?
Yes
Perform repair or diagnosis according to available Service Information.
• If vehicle is not repaired, go to next step.
No
Go to next step.
4
VERIFY CURRENT INPUT SIGNAL STATUS - IS CONCERN INTERMITTENT OR CONSTANT
• Start the engine.
• Access ECT, TP and MAF PIDs using WDS or equivalent.
• Warm up the engine until ECT PID is above 80 °C {176 °F}
• Drive the vehicle.
• Read TP PID while MAF PID is above 58.3 g/s {7.7 lb/min.}.
• Is TP PID reading above 12.5%?
Yes
Go to Step 7.
No
Go to next step.
5
VERIFY TP PID
• Start engine.
• Access TP, MAF and RPM PIDs using WDS or equivalent.
• Read TP PID while MAF PID is below 4.8 g/s {0.6 lb/min.} and RPM PID is above 500 rpm.
• Is TP PID reading above 50%?
Yes
Go to Step 12.
No
Go to 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 accordance with driving condition?
Yes
Intermittent concern exists. Go to INTERMITTENT CONCERNS troubleshooting procedure.
No
Inspect Mass airflow sensor and related circuits and terminals.
Repair or replace as necessary, then go to Step 16.
7
INSPECT TP SENSOR TERMINALS FOR ELECTRICAL CORROSION
• Turn ignition key to OFF.
• Disconnect TP sensor connector
• Inspect 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 next step.
8
VERIFY TP SENSOR
• Does TP sensor resistance smoothly change while gradually opening throttle valve?
Yes
Go to next step.
No
Replace TP sensor, then go to Step 11.
9
INSPECT PCM TERMINALS FOR ELECTRICAL CORROSION
• Disconnect PCM connector.
• Inspect 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 next step.
10
INSPECT CONSTANT VOLTAGE SUPPLY AND TP SIGNAL CIRCUITS FOR VOLTAGE DROP
• Turn ignition key to ON (Engine OFF).
• Inspect voltage between following terminals:
- TP sensor connector terminal C (harness-side) and PCM terminal 2K
- TP sensor connector terminal B (harness-side) and PCM terminal 2A
• Is voltage approx. 0 V?
Yes
Go to next step.
No
Inspect for rust or corrosion on PCM terminals 2A and 2K (harness-side).
• Repair or replace suspected terminal then go to next step.
11
VERIFY TROUBLESHOOTING OF DTC P0121 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Start the engine.
• Clear DTC from PCM memory using WDS or equivalent.
• Access ECT, TP and MAF PIDs using WDS or equivalent.
• Warm up the engine until ECT PID reading is above 80 °C {176°F}.
• Drive the vehicle and read TP and MAF PIDs.
• Verify PIDs reading are within specifications
MAF PID: above 58.3 g/s {7.7 lb/min.}
TP PID: above 12.5% above 5 s
• Is PENDING CODE of same DTC present?
Yes
Replace PCM, then go to Step 17.
No
Go to Step 17.
12
INSPECT TP SENSOR TERMINALS FOR ELECTRICAL CORROSION
• Turn ignition key to OFF.
• Disconnect TP sensor connector.
• Inspect 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 next step.
13
INSPECT GROUND CIRCUIT FOR VOLTAGE DROP
• Inspect resistance between TP sensor terminal A (harness-side) and body ground.
• Is resistance approx. 0 ohm ?
Yes
Go to next step.
No
Repair or replace for rust or corrosion on PCM terminal 2H (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 next step.
No
Replace TP sensor, then go to Step 16.
15
INSPECT PCM TERMINALS FOR ELECTRICAL CORROSION
• Disconnect PCM connector.
• Inspect for electrical corrosion on PCM and PCM connector male and female terminals.
• Is any electrical corrosion found?
Yes
Repair terminal, then go to next step.
No
Go to next step.
16
VERIFY TROUBLESHOOTING OF DTC P0121 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Start engine.
• Clear DTC from PCM memory using WDS or equivalent.
• Access RPM, TP and MAF PIDs using WDS or equivalent.
• Verify TP PID is reading below 50% while MAF PID is below 4.8 g/s {0.6 lb/min.} and RPM PID is above 500 rpm.
• Is PENDING CODE of same DTC present?
Yes
Replace PCM, then go to next step.
No
Go to next step.
17
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to applicable DTC troubleshooting.
No
Troubleshooting completed.