06 CDI with "Ck component B4/6 (Rail pressure sensor). The signal voltage is too low" - PeachParts Mercedes-Benz Forum

engatwork · #1 11-26-2017, 03:04 PM

Got the listed car (105k miles) in the shop with this code. Found #4 injector seal leaking and the beginning of black death. Took care of that and now I'm making an attempt to diagnose the low voltage fault code . I've checked the supply voltage to the sensor and it is 5 volts like it is supposed to be. On Autel items in error under the high pressure system is Fuel Rail Pressure Control Valve signal at 22.9% (range at idle is supposed to be 24-30)and Y94 Quantity Control Valve at 26.8% (supposed to be 37-42). I've narrowed it down to either of these two valves OR the in tank fuel pump. When driving the car I don't really see much movement on the quantity control valve position but that may be because it is in limp mode. Now the code will not clear even without starting the car. Prior to getting to this condition the car would run out good/strong when not in limp mode.

When the car first came in I was getting the code every now and then and these pressures were at 29.3% and 39.9% but the rail pressure was out of spec at 360 (min is 449 bar).

Has anyone run into this issue? Any thoughts/suggestions.

tia

engatwork · #2 11-27-2017, 05:53 PM

Now when I start the car (in park) the % signal from Y94 quantity control valve never moves when revving the engine. Rail pressure goes up and the pressure sensor signal changes though. I still need to check in tank fuel pump pressure.

ROLLGUY · #3 11-28-2017, 07:32 PM

I just checked mine, and here is what I found. Pressure control valve is 29.6%, Y94 quantity control valve is 41.4-41.7% rail pressure is 331-334 bar. All numbers are at idle and at operating temp. When revving, the numbers change. I hope this helps......Rich

Grzpdlr · #4 11-28-2017, 09:52 PM

I recently got Code 2047 - low rail pressure and the car actually stalled. I changed the fuel filter and , after 5 or 6 starts, the CEL went off. The car had 90k and I suspect this was the original filter.

engatwork · #5 11-29-2017, 06:00 AM

Thanks everyone. I've about ruled it to be a wiring issue seeing as how initially it was only happening occasionally but after I disconnected/reconnected the quantity control valve and the pressure sensor it won't even reset. I'll be opening up the harness in the area of the valve/sensor to see if I can find anything obvious.