Circuit Description
The Throttle Position sensor is potentiometer. A 5 volt reference is provided on CKT 1688 and ground is provided on CKT 808. The TP sensor signal CKT 417 varies between ground and 5 volts based on the position of the throttle plates. At low throttle angle, the TP sensor signal voltage is low. The PCM uses TP sensor information to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. DTC P0122 sets when the PCM detects a TP sensor signal that is too low. The PCM tests the TP sensor feedback every 100 ms. If the TP sensor reading is 0.1 volts or less, such as when the signal is open or shorted to ground, the PCM sets DTC P0122.
Conditions for Setting the DTC
Test Condition
Engine speed 600 RPM or greater.
Failure Condition
The TP sensor reading is 0.1 volts or less.
Action Taken When the DTC Sets
| • | PCM disables the torque converter clutch. |
| • | PCM calculates a TP sensor value based on MAP and engine speed inputs. |
| • | PCM disables fourth gear. |
| • | The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
With TP sensor or wiring open, TP sensor display will read 0.1 volts or less.
-
Checking for open TP sensor or open wiring. If the display value stays less than 4.96 volts with the TP sensor terminals A and C jumpered together, the problem is in the wiring.
-
Voltage should be greater than 0.5 volt if CKT 1688 is not open or shorted to ground.
-
If voltage at TP sensor connector terminal A is 4.5 volts or more, CKT 417 could be shorted to ground.
-
Use the MAP display to determine if a 5 volt reference problem exists.
-
If there is high resistance, CKT 417 could be open. If low resistance exists on CKT 417 the PCM may be faulty.
-
Checking the 5 volt reference feed to the TP sensor. The EGR, BBV and MAP 5 volt reference circuits must also be checked for a short to ground which could cause this DTC to set.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
Does throttle position read the same or less than the value specified? | 0.1 volts | Fault not present. Refer to Diagnostic Aids | ||
Does TP display read the same or more than the value specified? | 4.5 volts | |||
Using DMM J 39200 measure voltage to ground on jumper. Is voltage less than the value specified? | 0.5 volts | |||
Is voltage the same or more than the value specified? | 4.5 volts | |||
Is the resistance the same or more then the value specified? | 10K ohms | |||
Measure the resistance between PCM connector C1 terminal 62 and TP sensor connector terminal A (harness side). Is the resistance the same or less than the value specified? | 5 ohms | |||
Is the resistance the same or less than the value specified? | 5 ohms | |||
9 | Repair short to ground in the TP Sensor Signal circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
10 | Repair the open in TP sensor 5 Volt Reference circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
11 | Repair the open in the TP Sensor Signal circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
12 | Repair the short to ground on the 5 Volt Reference circuit, including from the splice to EGR valve and possibly the EGR valve itself. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
13 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
14 | Replace the Throttle Position sensor. Refer to TP Sensor Replacement . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
15 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
16 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
