DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Buick GL7 (Export) 2000

For 1990-2009 cars

### Circuit Description

The throttle position (TP) sensor circuit provides a voltage signal that changes relative to the throttle blade angle. The signal voltage will vary from less than 1.0 volts at closed throttle to more than 4.0 volts at wide open throttle (WOT). DTC P0123 will set when the powertrain control module (PCM) detects an excessively high signal voltage on the TP sensor signal circuit.

### Conditions for Running the DTC

The ignition is on.

### Conditions for Setting the DTC

• | The TP sensor signal voltage is more than 4.9 volts.

• | The above conditions are present for more than 10 seconds.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

• | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared with the scan tool.

### Diagnostic Aids

Inspect for the following conditions:

• | Poor connection at the PCM. Inspect the harness connectors for the following conditions:

• | Backed-out terminals

• | Improper mating

• | Broken locks

• | Improperly formed or damaged terminals

• | Poor terminal-to-wire connections

• | Use a corresponding mating terminal to check for the proper terminal tension.

• | A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the TP sensor display on the scan tool while moving the connectors and the wiring harnesses related to the TP sensor. A change in the display will indicate the location of the malfunction.

• | A malfunctioning TP sensor. With the key ON and the engine not running, observe the TP sensor display on the scan tool while slowly depressing the accelerator to WOT. If a voltage over 4.71 volts is measured at any point in normal accelerator travel, replace the TP sensor.

If DTC P0123 cannot be duplicated, the information included in the Failure Records data can be useful in determining the vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage diagnostic chart may isolate the cause of the malfunction.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Components that share the TP sensor 5 volt reference A circuit include the following devices:

• | The EGR valve

• | The engine oil pressure sensor

• | The MAP sensor. Disconnect these components one at a time while observing the TP sensor display on the scan tool. If the reading changes drastically when one of these components is disconnected, replace the component that affected the reading.

2. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read-only memory (EEPROM). If the PCM is replaced, the new PCM must be programmed.

#### DTC P0123 - TP Sensor Circuit High Voltage

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn ON the ignition switch.
2. With the throttle closed, observe the TP sensor display on the scan tool.

Is the TP sensor voltage more than the specified value?

4.7 V

Go to Step 4

Go to Step 3

3

1. Turn ON the ignition switch.
2. Review and record the scan tool Failure Records data.
3. Operate the vehicle within the Failure Records conditions as noted.
4. Using a scan tool, monitor the Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

Go to Step 4

Go to Diagnostic Aids

4

1. Turn OFF the ignition.
2. Disconnect the TP sensor.
3. Turn ON the ignition, leaving the engine OFF.
4. With a scan tool, observe the TP voltage parameter.

Does the TP sensor voltage equal the specified value?

0 V

Go to Step 5

Go to Step 8

5 | Using a digital multimeter (DMM), measure the voltage between the 5 volt reference circuit of the TP sensor and a known good ground. Does the voltage equal the specified value? | 5.0 V | Go to Step 6 | Go to Step 9
6 | Connect a test lamp between the ground circuit of the TP sensor and B+. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 7

7

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Test the ground circuit of the TP sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

8 | Test the signal circuit of the TP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
9 | Test all 5 volt reference A circuits and the connected components for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
10 | Inspect for poor connections at the harness connector of the TP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12
11 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
12 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Step 14 | --

14

1. Review and record the scan tool Failure Records data.
2. Clear the DTCs.
3. Operate the vehicle within the Failure Records conditions.
4. Using a scan tool, monitor the Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

Go to Step 4

System OK