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2006 Ram 1500 5.7L Hemi Stuck in Limp Mode: P0642, P2122, P0522, P0335 Diagnosis and Fix

Model: 2006 Ram 1500 5.7 Hemi Fault Code: P0335 Posted: 2017-09-07 02:26

My 2006 Ram 1500 5.7L Hemi is currently stuck in limp mode with no throttle response. The check engine light is on and the vehicle displays multiple fault codes: P0642 (Sensor Reference Voltage Low), P2122 (Accelerator Pedal Position Sensor Circuit Low Voltage), P0522 (Low Engine Oil Pressure), and P0335 (Crankshaft Position Sensor Circuit). The issue is intermittent — sometimes the truck will crank and run for about 10 minutes before returning to limp mode. I've recently replaced a valve cover gasket, but after that, the engine takes longer to start and has started exhibiting these symptoms. I’ve tested the 5V reference voltage at the oil pressure sensor and found no signal on the pink/yellow wire. The oil pressure gauge is also not reading correctly. Based on community advice, I suspect a shorted sensor or wiring issue affecting the 5V reference circuit. I've tried unplugging sensors one by one to isolate the fault, and discovered that disconnecting the oil pressure sensor restored voltage to the accelerator pedal sensor. After replacing the oil pressure sensor and cleaning the throttle body with brakeleen and IPA, the codes cleared and the truck now runs smoothly with full throttle response. This suggests that a shorted oil pressure sensor was pulling the 5V reference circuit to ground — a common issue in 2006 Ram Hemi models.

Related fault codes
P0335P0522P0642P2122
Comments (13)
Anonymous 2017-09-07 07:33

Have you performed any recent repairs or modifications? Please share details about any work done, aftermarket parts installed, and whether you're using a wiring diagram or digital multimeter (DVOM) for diagnostics.

Anonymous 2017-09-07 08:03

The vehicle reports low voltage inputs from the accelerator pedal sensor, oil pressure sensor, and crankshaft position sensor. I recommend testing each sensor individually to determine if one is faulty or causing a circuit short.

Anonymous 2017-09-07 08:12

Please share your repair history and any modifications. A systematic diagnostic approach using a wiring diagram and DVOM is essential — the issue could be a sensor, wiring harness, or PCM. I can provide a detailed wiring schematic and step-by-step testing instructions if needed.

Anonymous 2017-09-07 08:18

The last major work was replacing a valve cover gasket several months ago. Since then, the engine has taken longer to crank and now exhibits limp mode issues — possibly related to electrical or mechanical stress on the system.

Anonymous 2017-09-07 08:47

Use a multimeter to probe the wire for voltage. Then, systematically disconnect each sensor and observe if the voltage returns. Also confirm whether you have a performance chip or tuning program — this could affect code interpretation.

Anonymous 2018-10-25 15:29

Has your issue been resolved? If so, how was it fixed on your 2006 Ram 1500 5.7L Hemi with P0642 and P2122 codes?

Anonymous 2018-10-26 05:55

A shorted sensor is the most likely cause — especially one pulling the 5V reference circuit to ground. It could also be a damaged 5V reference wire or a faulty PCM. Before replacing the PCM, verify power and ground connections using a multimeter and wiring schematic. I can provide a detailed diagram and testing guide.

Anonymous 2018-10-26 09:45

I’ve tested the 5V supply to the accelerator pedal (APP) sensor — no voltage is present on the pink/yellow wire, which should be the 855 5V reference. Additionally, my oil pressure gauge isn’t reading at all.

Anonymous 2018-10-27 06:47

The PCM has two separate 5V reference circuits. Back-probe each one to verify if you have 5 volts. Try disconnecting the oil pressure sensor connector — if voltage returns on the APP sensor’s 5V line, this confirms a shorted sensor or wiring issue.

Anonymous 2018-11-08 10:46

In my previous repair of a similar 2006 Ram Hemi, the wiring harness behind the transmission dipstick tube was stretched and causing intermittent shorts. Re-routing it to a front position resolved the issue — though the customer was advised to replace the harness permanently.

Anonymous 2018-11-08 13:02

I found that the oil pressure sensor was shorted to ground. By tracing the pink/yellow wire and unplugging each sensor, I restored voltage. After replacing the sensor, the truck runs normally — thanks to all the helpful troubleshooting tips.

Anonymous 2018-11-08 13:35

Thanks for sharing your solution! Since your oil pressure gauge wasn’t working, it was likely a shorted oil pressure sensor pulling the 5V reference to ground. This is a known issue in many 2006 Ram Hemi models — often due to moisture or dirt inside the sensor connector. Wiring or PCM issues are less common but possible.

Anonymous 2020-02-21 11:50

Thank you all for your input! My truck started sputtering one morning, and I discovered that the back of the oil pressure sensor had gotten wet and dirty — moisture combined with debris caused a short. After unplugging and cleaning the sensor connection with contact cleaner and a nylon-bristled brush, I also cleaned the throttle body with brakeleen and IPA. I disconnected the battery for 2 minutes to discharge residual voltage before reconnecting. After retesting, all error codes cleared. The truck started immediately and accelerated smoothly — especially noticeable when climbing hills from 70 to 80 mph. This confirms that sensor contamination was the root cause. My truck is a 2007 Ram TRX4 with a 5.7L Hemi engine.