| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. | 
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. | 
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. | 
Circuit  | Short to Ground  | High Resistance  | Open  | Short to Voltage  | Signal Performance  | 
|---|---|---|---|---|---|
APP Sensor 1 - 5-Volt Reference  | P0698, P2122, P2564  | P2138  | P2122  | P0699, P2123, P2227  | --  | 
MAP Sensor - 5-Volt Reference  | P0698, P0107  | P0101  | P0107  | P0699, P0106  | --  | 
TC Vane Position Sensor - 5-Volt Reference  | P0698, P2564  | P2563  | P2564  | P0699, P2565  | --  | 
EGR Valve - 5-Volt Reference  | P0698  | P046C  | P0405  | P0699, P0401  | --  | 
These 5-volt reference circuits are independent of each other outside the engine control module (ECM), but are bussed together inside the ECM. Therefore, a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The ECM monitors the voltage on the 5-volt reference circuit.
| • | The ignition is ON. | 
| • | Diagnostics run continuously. | 
| • | The ECM detects the 5-volt reference 3 circuit voltage is less than 4.7 volts. | 
| • | The above condition is present for 2 seconds. | 
| • | The ECM detects the 5-volt reference 3 circuit voltage is more than 5.2 volts. | 
| • | The above condition is present for 2 seconds. | 
| • | 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/Failure Records. | 
| • | 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. | 
| • | Clear the MIL and the DTC with a scan tool. | 
| ⇒ | If the voltage measures 4.7-5.2 volts, replace the APP sensor . | 
| ⇒ | If voltage changes when one of the above components are disconnected, replace the component. Refer to the appropriate replacement procedure. | 
| ⇒ | If no problem was found in the 5-volt reference 3 circuit , replace the ECM. | 
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |