P1121

DTC P1121 Throttle Position (TP) Sensor Circuit - Intermittent High Input:

Throttle Position (TP) Sensor Circuit:

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

The TP signal is one of the most important inputs used by the Vehicle Control Module-A (VCM-A) for fuel control and for most of the VCM-A control outputs.

On the nonadjustable TP sensor, each time voltage drops below 1.25 volts and stops, the VCM-A assumes this value as 0 throttle angle and measures percent throttle from this point on. DTC P1121 is a type "D" DTC.

DTC P1121 WILL SET WHEN
^ Key "ON," engine "OFF"
or
^ Key "ON," engine "ON"
and
^ TP sensor signal voltage is greater than 4.9 volts.

ACTION TAKEN (VCM-A WILL DEFAULT TO)
The VCM-A will store DTC P1121 to history if an intermittent problem is detected.

DTC P1121 WILL CLEAR WHEN
The VCM-A will turn the MIL "OFF" after three consecutive trips without a fault condition present. A history DTC will be cleared if no fault conditions have been detected for forty warm-up cycles [coolant temperature has risen 22°C (40°F) from start-up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle] or the Tech 1 clearing feature has been used.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If TP signal is greater than 4.8 volts, then the fault is present.
2. With the TP sensor disconnected, the TP signal voltage should go low if the VCM-A and wiring is OK.
3. Probing CKT 452 with a test light checks the 5 volt return circuit. This step isolates a faulty sensor, VCM-A or an open CKT 452.

DIAGNOSTIC AIDS
A Tech 1 scan tool reads throttle position in volts. Should read about 0.45 to 0.85 volt with throttle closed and ignition "ON" or at idle. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).

Also, some Tech 1 scan tools will read throttle angle 0% = closed throttle 100% = WOT

Scan TP sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from below 1.25 volts (1250 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at Wide Open Throttle (WOT) position.

A DTC P0123 will result if CKT 452 is open or CKT 417 is shorted to voltage.

Refer to Intermittents. - Intermittent Malfunctions