Vehicle: 2009 Dodge Grand Caravan, V6-3.8L, Automatic Transmission/Transaxle
Problem: The vehicle was brought to the shop because of poor acceleration and a hesitation. The malfunction indicator light (MIL) was on.
Case Details: The technician connected a scan tool and retrieved the following active diagnostic trouble code (DTC): P2127 - Accelerator Pedal Position Sensor Circuit Low
Based on the DTC, he decided to replace the accelerator pedal assembly, which included the accelerator pedal position (APP) sensor, the throttle body and the crankshaft position (CKP) sensor. After replacing those parts there was no improvement and the MIL came back on within minutes.
A quick call to ALLDATA Tech-Assist gave the technician some background information and a solid diagnostic strategy. The Tech-Assist consultant told the technician that the APP sensor on this vehicle had two separate 5-volt references and ground circuits. The throttle body and CKP sensor both share the APP1 circuit, not the APP2 circuit.
Since the DTC was for the APP2 circuit, the technician should test K856 (YEL/PNK) for 5 volts and K400 (BRN/VIO) for ground. If there was a 5-volt reference problem, other components in that circuit such as the exhaust gas recirculation valve, manifold absolute pressure sensor, camshaft position (CMP) sensor and the transmission line pressure sensor could be causing problems for the APP2.
The technician found no voltage on the 5-volt reference circuit at the APP2 wire. He tested all the components in that circuit and found the CMP sensor was shorting the 5-volt reference to ground. Once unplugged, the 5-volt reference returned at the APP2 wire.
Confirmed Repair: The technician installed a new CMP sensor, cleared the DTC, and took the vehicle for a test drive. The MIL did not light up and the engine ran great. Problem solved!