A customer brought their 2017 Dodge Ram 1500 into the shop because the malfunction indicator light (MIL) was on, the idle speed was fluctuating, and there was a lack of throttle response. The customer stated that the drivability. The customer stated that the drivability issues were intermittent.
Case details
After a test drive to verify the problem, the technician connected a scan tool and pulled the following diagnostic trouble codes (DTCs):
- P0653: Sensor Reference Voltage 2 Circuit High
- P2127: Accelerator Pedal Position Sensor 2 Circuit Low
- P2181: Cooling System Performance
- P2681: Engine Coolant Bypass Valve Control Circuit Open
With the scan tool, he checked the accelerator pedal position voltages and found 5.02 volts on both 5VREF circuits at the accelerator pedal. To expedite further diagnosis, the technician called an ALLDATA Tech-Assist consultant.
The consultant advised that the 5-volt circuit was connected to the manifold absolute pressure (MAP) sensor, camshaft position sensors one and two (CMP1 and CMP2), accelerator pedal position (APP) sensor, fuel rail pressure sensor, and the coolant temperature bypass valve.
Since the coolant temperature bypass valve also has a 12-volt power supply going to it, there is more of a chance of it spiking the 5-volt reference circuit if it's shorted. He further advised starting the diagnosis by disconnecting the coolant temperature bypass valve to see if the symptoms subside.
As soon as the technician disconnected the coolant temperature bypass valve, the symptoms disappeared.
Confirmed repair
The coolant temperature bypass valve was replaced, and then the technician cleared the codes and took the truck out for a good road test. The engine ran perfectly, and the MIL remained off. Problem solved!
