Circuit Description
Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt at idle to greater than 4 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by control module for fuel control and for most other control module control outputs. Code inhibits TCC and 4th gear.
Note. Test numbers refer to numbers on diagnostic chart.
- Determines if conditions necessary to set code exist.
- Simulates Code P0123 (high voltage). If control module recognizes high signal voltage, control module and wiring are okay.
- Simulates a high signal voltage. Checks signal circuit for an open.
Code P0122 3.8L "U" Body - Circuit Diagram. Scheme 52
Tech 1 displays throttle position in volts. Voltage should increase steadily as throttle is moved toward WOT.
An open or short to ground in reference and signal circuits will cause code to set. Check for
Inspect control module harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
Monitor TP sensor voltage display on Tech 1 while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.
Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TP sensor voltage when throttle is closed (less than 1.25 volts) to greater than 4.5 volts when throttle is held at WOT position.
Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt at idle to about 5 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by PCM for fuel control and for most of PCM control outputs. Code inhibits TCC and 4th gear.
Code P0123 will set when the following conditions are present.
- TP sensor voltage is greater than 4.8 volts at any time, or engine is running and airflow is less than 17 grams per second.
- Engine speed is greater than 600 RPM.
- TP sensor signal voltage is greater than 1.06 volts.
- Code P0101 is not present.
- All conditions are met for 5 seconds.
Note. Test numbers refer to numbers on diagnostic chart.
- With closed throttle, ignition on or idling, voltage at PCM TP sensor signal circuit should be about .20-.74 volt.
- With TP sensor disconnected, TP sensor voltage should decrease and Code P0122 will set. This test verifies that PCM and wiring are okay.
- Probing ground circuit with a test light check sensor ground circuit. A faulty sensor ground circuit will cause Code P0123 to set.
Code P0123 "A", "C", "G", "H" & "W" Bodies - Troubleshooting Diagram. Scheme 53
Scan tester displays throttle position in volts. With closed throttle, ignition on, or at idle, voltage should be about .20-.74 volt. If voltage is not as specified, replace TP sensor. An open in sensor ground circuit will cause Codes P0112, P0712, P0117 and P0123 to set. Check for
Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
Monitor TP sensor voltage display on scan tester while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.
Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TP sensor voltage when throttle is closed (about .20-.74 volt) to greater than 4 volts when throttle is held at WOT position.
Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt or at idle to approximately 5 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by control module for fuel control and for most other control module control outputs. On non-adjustable TPS sensors, each time voltage drops below 1.25 volts and stops, control module assumes this value as 0 throttle angle and measures percent throttle from this point on. Code inhibits TCC and 4th gear.
Note. Test numbers refer to numbers on diagnostic chart.
- With closed throttle, ignition on, or at idle, voltage at control module TP sensor signal circuit should be .20-.74 volt.
- With TP sensor disconnected, TP sensor voltage should decrease and Code P0122 will set. This test verifies that control module and wiring are okay.
- Probing ground circuit with a test light check sensor ground circuit. A faulty sensor ground circuit will cause Code P0123 to set.
Code P0123 3.8L "U" Body - Troubleshooting Diagram. Scheme 54
Tech 1 displays throttle position in volts. With closed throttle, ignition on, or at idle, voltage should be .20-.74 volt. If voltage is not as specified, replace TP sensor. An open in sensor ground circuit will cause Codes P0112, P0712, P0117 and P0123 to set. Check for
Inspect control module harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
Monitor TP sensor voltage display on Tech 1 while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.
Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TP sensor voltage when throttle is closed (.20-.74 volt) to greater than 4 volts when throttle is held at WOT position.
Vehicle Speed Sensor (VSS) in transaxle provides vehicle speed information to PCM. Voltage level and number of pulses increase with vehicle speed. PCM converts pulsing voltage to MPH, and MPH can be displayed using a scan tester.
Function of VSS buffer, used in past models, has been incorporated into PCM. PCM supplies necessary signal for instrument cluster (4004 pulses per mile) for operating speedometer and odometer.