Circuit Description
The DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage diagnostic monitors the TP sensor signal. The TP sensor is a potentiometer whose resistance value changes along with the throttle valve position. The powertrain control module (PCM) provides a 5-volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and uses the voltage to calculate the percentage of throttle valve opening. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored by the PCM increases. The TP sensor resistance increases when the throttle valve opening decreases, therefore the voltage being monitored by the PCM will decrease.
Throttle Opening | TP Resistance | TP Percentage | TP Signal Voltage |
|---|---|---|---|
Large | High | High | High |
Small | Low | Low | Low |
Condition for Running the DTC
The ignition is ON or the engine is running.
Conditions for Setting the DTC
| • | A low voltage TP sensor input is indicated at the PCM. |
| • | The above condition is present for at least 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
| • | The PCM enters the Failsafe mode and assumes the engine throttle valve angle is 24.5 degrees. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing cycles without a fault present. |
| • | A history DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Perform the scan tool clear DTC Information function in order to clear the DTC. |
Diagnostic Aids
On a cold engine the TP sensor may indicate 3 percent or more with the throttle closed at idle. After the engine warms up and the plunger of the fast idle-up valve has retracted, the TP sensor will indicate 0 percent at idle.
If a DTC P0122 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0122 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0122 appears in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has not yet run. When the DTC P0122 does not appear in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has run. If the MIL is NOT illuminated, and there is no DTC Status in DTC Information, the DTC P0122 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.
An intermittent malfunction may be caused by a fault in the TP sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
If the DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio.
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When the 5-volt reference is jumpered to the TP input circuit, the scan tool parameter should read 99 percent.
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When the TP sensor input circuit is jumpered to battery voltage , the scan tool parameter should read 99 percent.
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The 5-volt reference circuit is shared internally in the PCM with the fuel tank pressure (FTP) sensor. Be sure to inspect the FTP sensor reference circuit for a short to ground.
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Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0122 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0122 appears in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has not yet run. When the DTC P0122 does not appear in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0122 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | ||
2 | Is there a DTC P0107 and DTC P0452 also set? | -- | Go to Step 9 | Go to Step 3 |
3 |
Does the TP sensor percentage steadily increase within the specified range? | 0 - 99% | Go to Step 4 | Go to Step 5 |
Did a DTC P0122 set? | -- | Go to Step 5 | Go to Diagnostic Aids | |
Does the TP sensor percentage equal the specified value? | 99% | Go to Step 11 | Go to Step 6 | |
Does TP sensor percentage equal the specified value? | 99% | Go to Step 7 | Go to Step 8 | |
7 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 10 |
8 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 10 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 | |
10 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 13 |
11 |
Was a repair necessary? | -- | Go to Step 14 | Go to Step 12 |
12 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 14 | -- |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 | |
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
