Pinpoint Test C: DTC P0121, P0122, P0123

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2008 Jaguar S-Type, 2007 Jaguar S-Type, 2006 Jaguar S-Type, 2005 Jaguar S-Type, and 2004 Jaguar S-Type. However, it is still accessible from the selected car via links, so may be relevant.

CHECK THE POWER SUPPLY TO THE THROTTLE POSITION SENSOR
Turn the ignition switch the to the RUN position.

Measure the voltage between the throttle position sensor electrical connector PI 26 pin 4 (OY) and ground.

Is the voltage less than 4.5 volts?

YES: Go to step 2..

NO: Go to step 4..
CHECK THE THROTTLE POSITION SENSOR POWER SUPPLY CIRCUIT FOR OPEN CIRCUIT
Turn the ignition switch to the OFF position.

Disconnect the ECM electrical connector PI 1 and the throttle position sensor electrical connector PI 26.

Measure the resistance between PI 1 pin 12 (OY) and PI 26 pin 4 (OY).

Is the resistance less than 5 ohms?

YES: Go to step 3..

NO: REPAIR the throttle position sensor power supply circuit from the ECM to the throttle position sensor. CLEAR the DTC. TEST the system for normal operation.
CHECK THE THROTTLE POSITION SENSOR POWER SUPPLY CIRCUIT FOR A SHORT TO GROUND
Measure the resistance between PI 26-pin 4 (OY) and ground.

Is the resistance greater than 10,000 ohms?

YES: DIAGNOSE the electronic engine control system. For additional information, refer to Electronic Engine Controls or Electronic Engine Controls .

NO: REPAIR the throttle position sensor power supply circuit from the ECM to the throttle position sensor. CLEAR the DTC. TEST the system for normal operation.
CHECK THE THROTTLE POSITION SENSOR GROUND CIRCUIT
Turn the ignition switch to the OFF position.

Disconnect the throttle position sensor electrical connector PI 26.

Measure the resistance between PI 26 pin 1 (BG) and ground.

Is the resistance less than 5 ohms?

YES: Go to step 6..

NO: Go to step 5..
CHECK THE THROTTLE POSITION SENSOR GROUND WIRE FOR OPEN CIRCUIT
Disconnect the ECM electrical connector PI I and the throttle position sensor electrical connector PI 26.

Measure the resistance between PI 26 pin 1 (BG) and PI 1 pin 19 (BG).

Is the resistance less than 5 ohms?

YES: Go to step 6..

NO: REPAIR the throttle position sensor ground circuit from the ECM to the throttle position sensor. CLEAR the DTC. TEST the system for normal operation.
CHECK THE THROTTLE POSITION SENSOR
Measure the resistance between PI 26 pin 2 and PI 26 pin 4.

Measure the resistance between PI 26 pin 3 and PI 26 pin 4.

Are the resistor values the same?

YES: Go to step 7..

NO: INSTALL a new throttle body. For additional information refer to Electronic Engine Controls or Electronic Engine Controls .
CHECK CONTINUITY OF THE THROTTLE POSITION SENSOR OUTPUT CIRCUIT
Measure the resistance between PI 1 pin 75 (R) and PI 26 pin 3 (R).

Measure the resistance between PI 1 pin 76 (Y) and PI 26 pin 2 (Y).

Is the resistance less than 5 ohms?

YES: Go to step 8..

NO: REPAIR the circuit from the ECM to the throttle position sensor. CLEAR the DTC. TEST the system for normal operation.
CHECK THE THROTTLE POSITION SENSOR OUTPUT CIRCUIT FOR A SHORT TO GROUND
Measure the resistance between PI 26 pin 3 (R) and ground.

Measure the resistance between PI 26 pin 2 (Y) and ground.

Is the resistance greater than 10,000 ohms?

YES: DIAGNOSE the electronic engine control system. For additional information, refer to Electronic Engine Controls or Electronic Engine Controls .

NO: REPAIR the circuit from the ECM to the throttle position sensor. CLEAR the DTC. TEST the system for normal operation.