Hi all,

I'm not sure if I am posting this correctly so please advise if I need to move this post somewhere else.
2010 3.0D XJ X351. I get MAF sensor error and restricted performance - coupled with MIL for the most part. I tested the MAF sensors, and I get 3V on bank B and just over 4V on bank A (the one with the extra wire / temp sensor). The readings (obvs wrong) NOT changing with engine speed at all (only change is between engine on or off but still constant). Swapping the connectors from one to the other carries the specific voltage on the other side indicating the sensor itself isn't giving that signal. Changed both sensors with originals and I get same voltages! This is killing me, I expect this is a wiring issue or ECU/ECM.

Little background: both manifolds cracked so I replaced them. Then I got absolute pressure errors and limp mode. I then bought a new map sensor and an evap tool, checked all leaks and sealed them (incl throttle body o-rings and clamps). Still had limp mode so took it to marshal jag. Instead of looking at my problem they just went on topix, looked at TB's and told me my CSOV (secondary) is gone - end of diagnostic.

I bought it and changed it. Now, only maf sensor error persists. Does anyone have any clue?

Many thanks in advance!

 

Hi Robertmpopa90

Note: The MAF:s on 3.0D are not Bank A / B configuration, because of Twin turbo settings, where only one turbo are used under 3000rpm (don´t remember the exact rpm) -> Only one MAF is used bellow that rpm. 2nd Turbo and MAF join the party in high rpms only. MAF:s are same, but wiring and voltage might not be? On botton front of the engine bay are the device blocking another air circuit when it is not in use. I think you have problem there and have backpressure for the 2nd MAF.
Check repair and service manual on sticky section. The system are well descripted there.

 

Hi Vasara, thank you for your reply!
If that was the case then when I clear all faults in the ECU with the engine off and then test the voltages I should get below a volt or around there? These values never change. Also, ylu are talking about the Secondary CSOV valve which I changed because it wouldn't hold vacuum thus wouldn t open the secondary turbo path.

 

MAF sensor uses digital signal, not a plain voltage. (Temp sensor uses voltage levels) You cant measure it with voltage meter.
From Repair and service manual. page 1437:
"The MAF sensor output is a digital signal proportional to the mass of the incoming air. The ECM uses this data, in conjunction
with signals from other sensors and information from stored fuelling maps, to determine the precise fuel quantity to be
injected into the cylinders. The signal is also used as a feedback signal for the EGR (exhaust gas recirculation) system."
and:
"The IAT sensor in the lower sensor incorporates a NTC (negative temperature coefficient) thermistor in a voltage divider circuit.
The NTC thermistor works on the principle of decreasing resistance in the sensor as the temperature of the intake air
increases. As the thermistor allows more current to pass to ground, the voltage sensed by the ECM decreases."

There are also re-circulation valve right next to the SCOV. Did you check that too?

 

This is easy to diagnose with JLR SDD setup. I just bought my XJ not long ago and had high fuel trims , turned out one of the maf was underreporting but no cel was triggered. Just have to log and monitor both maf signals separately.
I Do loan out Dealers laptop setup if you need and can help remote diagnose it for you. Also we can do a performance tune on the XJ, car becomes a beast . Currently near 600 hp on mine with all stock , only ECU tuned