P1220

Schematic:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor is pan of the throttle body assembly. The TP sensor is actually 2 individual sensors within one housing. The TP sensor 1 is the main input to the Engine Control Module (ECM) for actual throttle positioning. Each of the TP sensors share a common 5 volt reference circuit and a reference ground circuit. The 5 volt reference circuit is also shared with Accelerator Pedal Position (APP) sensor 2. The 5 volt reference voltage is supplied on two separate ECM terminals, but the terminals are connected internally to the same voltage supply. The TP sensor 1 signal circuit is pulled up near 5 volts in the ECM and the signal circuit for TP sensor 2 is referenced to ground. This causes each TP sensor to have opposite functionality. The TP sensor 1 signal voltage increases as the throttle opens, from below 1.0 volt at 0 percent throttle to above 4.0 volts at 100 percent throttle. The TP sensor 2 signal voltage decreases from around 4.0 volts at 0 percent throttle to below 1.0 volt at 100 percent throttle.

CONDITIONS FOR RUNNING THE DTC
The battery voltage is more than 7.0 volts.
The engine is running.

CONDITIONS FOR SETTING THE DTC
^ The TP sensor 2 voltage is less than 0.156 volt or more than 4.8 volts.
^ The difference between TP sensor 1 and TP sensor 2 is more than 13 percent.
^ One of the above conditions is met for 140 ms (0.140 seconds).

ACTION TAKEN WHEN THE DTC SETS
^ The ECM illuminates the Malfunction Indicator Lamp (MIL) on the first drive trip that the diagnostic runs and fails.
^ The ECM attempts to record the operating conditions in the Freeze Frame.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The ECM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and passes.
^ A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
^ The scan tool clears the MIL/DTC.

DIAGNOSTIC AIDS
The ECM compares the signal of each of the throttle position sensors to each other throughout the entire range of the throttle plates. The ECM also compares the signal of the throttle position sensors to other sensors when the engine is running to determine if the sensor readings are correct. Clear the DTCs and actuate the throttle through the entire range with the ignition ON and the engine OFF and also with the engine running. If the DTC resets, check all of the circuits to the throttle position sensors for high resistance. Resistance as low a 2 ohms in the TP sensor circuits can affect the operation of the sensors. Test the reference ground circuit of the TP sensors for a short to ground. The reference ground circuit is provided by the ECM and an external short to ground will affect the operation of the sensors. The reference ground is shared with other components so any faults on this circuit can affect the operation of the entire engine controls system. Refer to Circuit Testing in Diagrams.

With the ignition ON and the engine OFF, view the TP sensor 1 and the TP sensor 2 with a scan tool. Slowly depress the accelerator pedal, the voltage on TP sensor 1 should increase steadily from 0.7 volt to about 4.2 volts. TP sensor 2 should move opposite from above 4.2 volts to about 0.6 volt. If one sensor value changes and the other does not, inspect the sensor circuits for high resistance or shorts. If the circuits are OK, replace the throttle body assembly.

Clear the DTCs and turn ON the ignition with the engine OFF for 30 seconds. If a DTC P1526 sets, this indicates there is still a problem with in one of the TP circuits or with the sensors.

Use the J 35616-A connector test adapter kit for any test that requires probing the ECM harness connector or a component harness connector.

Refer to Testing for Intermittent and Poor Connections in Diagrams for Intermittent conditions.

TEST DESCRIPTION

Steps 1 - 8:

Steps 9 - 19:

Steps 20 - 29:

The numbers below refer to the step numbers on the diagnostic table.
4. The ECM performs a comparison of the signals from both throttle position sensors during the entire range of operation. If the DTC does not set with the key on and the accelerator pedal released, actuating the throttle may cause the DTC to set.
5. Use the Engine Speed Control function located under TAC System in the scan tool menu to increase the engine RPM. This DTC requires engine RPM and throttle position to be off idle in order for the diagnostic to run.
8. This step tests the integrity of the TP sensor 2 signal circuit. The TP sensor 2 data parameter should read near 5 volts when connected to the 5 volt reference circuit.
9. This step is to test the integrity of the reference ground circuit through the ECM. A small amount of current will appear on this circuit when the ECM is operational. The measured resistance of this circuit will increase when the ECM is operational. This is considered normal.
12. The 5 volt reference for the TP sensors and APP sensor 2 are connected inside the ECM. This step is to determine if the APP sensor is affecting the 5 volt reference circuit of the TP sensors.
18. The 5 volt reference for the TP sensors and APP sensor 2 are connected inside the ECM. A short to voltage on the 5 volt reference circuit of APP sensor 2 will affect the 5 volt reference circuit of the TP sensors.
19. The 5 volt reference for the TP sensors and APP sensor 2 are connected inside the ECM. A short to ground on the 5 volt reference circuit of APP sensor 2 will affect the 5 volt reference circuit of the TP sensors.
20. Additional resistance in any one of the throttle position sensor circuits can effect the operation of the sensors.
21. Additional resistance on the reference ground circuit can affect the operation of the sensors.