P1121

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor provides a voltage signal which changes relative to the throttle blade angle. The signal voltage varies from about 0.5 volt at idle to about 4.0 volts at Wide Open Throttle (Wide Open Throttle (WOT)).

The TP signal is one of the most important inputs used by the VCM for fuel control and for most of the VCM control outputs. This DTC is a type D DTC.

CONDITIONS FOR SETTING THE DTC
The DTC sets when the TP sensor signal voltage is greater than about 4.8 volts and the MAP is less than 51 kPa for a period greater than 4 seconds with engine running.

ACTION TAKEN WHEN THE DTC SETS
The VCM stores the DTC to the history if the VCM detects an intermittent problem.

CONDITIONS FOR CLEARING THE MIL/DTC
The VCM turns the Malfunction Indicator Lamp (MIL) off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

DIAGNOSTIC AIDS
The VCM pins GR 12 and GR 27 are spliced together inside the VCM. When checking one of these circuits for a problem, also check the other circuit and the components on the circuit. The scan tool reads the throttle position in volts. The scan tool should read about 0.45 to 0.85 volt with the throttle closed and the ignition switch turned ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward the Wide Open Throttle (WOT).

Also, some scan tools will read the throttle angle. 0% = closed throttle. 100% = WOT

Scan the TP sensor while depressing the accelerator pedal with the engine turned off and the ignition turned on. The display should vary from below the 1.25 volts (1250 mV) when the throttle was closed to over 4.5 volts (4500 mV) when the throttle is held at WOT position.

A DTC P0123 will result if the TP ground circuit is open or the TP signal circuit is shorted to the voltage.

A DTC P0122 will result if an open or a short to ground in the 5 volt reference circuit or the TP sensor signal circuit.

Refer to Intermittents.

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.

2. If the TP signal is greater than 4.8 volts, then the fault is present.
3. With the TP sensor disconnected, the TP signal voltage should go low if the VCM and wiring is OK.
4. Probing the TP sensor ground circuit with a test lamp checks the 5 volt return circuit. This step isolates a faulty sensor, VCM or an open TP sensor ground circuit.