P1220

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signals, low reference circuits, and 5-volt reference circuits are used to connect the TP sensor assembly to the Throttle Actuator Control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to reference voltage as the throttle opens, from below 1.0 volt at closed throttle to above 3.5 volts at Wide Open Throttle (WOT). The TP sensor 2 signal voltage is pulled down to low reference from around 3.8 volts at closed throttle to below 1.0 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out-of-range condition is detected with the TP sensor 2, this DTC will set and the Reduced Engine Power message will be displayed.

TP Sensor Position Table:

The table shows the percentage and voltage readings of the scan tool based on the position of the TP.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P1517 and P1518 are not set.
^ The ignition switch in the crank or run position.
^ The ignition voltage is greater than 5.23 volts.

CONDITIONS FOR SETTING THE DTC
^ The TP sensor 2 voltage is less than 0.13 volts, or greater than 4.87 volts.
^ All of the above conditions exist for less than 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
^ The control module commands the TAC system to operate in the Reduced Engine Power mode.

OR

^ Under certain conditions the control module commands the engine OFF.
^ The message center displays Reduced Engine Power.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
^ Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs could be set without circuit or component conditions found during diagnostic testing.
^ When the TAG module detects a condition within the TAC system, more than one TAG system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Be aware of this if you review the stored information in Capture Info.
^ If this DTC is determined to be intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-5:

Steps 6-14:

Steps 15-23:

Steps 24-34:

The numbers below refer to the step numbers on the diagnostic table.
12. Using a test lamp reduces the amount of current fed into the signal circuit. The scan tool should display the maximum value for this parameter, 5 volts, ever though the actual voltage is higher.
18. The TP 2 sensor and the APP 2 sensor share a common 5-volt reference. The 5-volt reference circuits are connected internally within the TAC module. Disconnecting the TAC module will isolate the 5-volt reference circuits.
19. The TP sensor 2 and the APP sensor 2 share a common 5-volt reference. A short to voltage on the APP sensor 2, 5-volt reference circuit will affect the TP sensor 2, 5-volt reference circuit.
34. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This condition is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting the components during testing may set additional DTCs. Be aware of this condition if you review the stored information in Capture Info.