New Owner! Tranmission cutting out on freeway :/

[OslosisJones]

Yep, pretty similar codes to before:

MAF signal and flow too low
-Damaged unit (MAF is supposedly new, I cleaned with CRC two weeks ago. Previous mechanic saw MAF codes and replaced entire unit, but this obviously didn't solve the problem and I doubt the MAF is at fault)
-Leaking in system
-Contaminated throttle body
-Blocked intake system

Fuel Pressure Sensor signal too high
-Short to ground circuit
-Damaged temperature sensor (?)

Fuel Pressure signal too high
-Damaged fuel pressure sensor
-Damaged fuel pump control


These problems could very well be causing some or all of the hesitation/surging/shuddering that has lead me to believe my transmission could be compromised.

I am definitely replacing fuel filter and spark plugs this weekend. Not sure what to do about MAF and fuel pressure codes. Don't have a manometer setup to test the fuel pressure.

Should I just go ahead and replace: filter->fuel pressure sensor-> MAF (in that order) until it stops throwing codes?

Where should I look for leaks/blockages in the intake system?

Should I bother pulling out the throttle body to clean/inspect?

Anything else I'm missing?

PDF of VIDA readout included for the curious/especially helpful!!

edit: Couldn't find the ETM test Howard mentions on his site, so I took some screen shots of the fuel pressure and throttle position sensors. If potentiometer 2 is supposed to read high (notice pot. 2 is scaled to 114%), then the throttle looks fine. Less sure about the fuel pressure sensor, it dropped down quite a bit after idling for 30 seconds or so.

Going to replace spark plugs, fuel filter, and lower transmission mount this weekend. If that doesn't do it then I'll bring it to an independent to help diagnose MAF/intake issues, Fuel pressure sensor, throttle, or axles/other drive components.

7-20-16 check engine light on.pdf

[youropeen]

Since you once again got the fuel pressure codes, I can guarantee that the pressure sensor is bad.

It's a very simple swap.

Part number 31272730 from your supplier of choice. I got the Bosch unit from FCP when I swapped mine out.

Supposedly you can source the exact same part through Land Rover but I have not found one for any cheaper than the one I linked to.

Seriously, start there.

[OslosisJones]

Since you once again got the fuel pressure codes, I can guarantee that the pressure sensor is bad.

It's a very simple swap.

Part number 31272730 from your supplier of choice. I got the Bosch unit from FCP when I swapped mine out.

Supposedly you can source the exact same part through Land Rover but I have not found one for any cheaper than the one I linked to.

Seriously, start there.

I'm inclined to agree, but would rather have this properly diagnosed before throwing parts at it. MAF codes are also showing even though I am almost certain that the MAF sensor is fine.

Severly fouled fuel filter could be the main culprit, makes some sense as I'm only seeing power loss/hesitation at relatively low throttle. At higher throttle the pump seems to be providing enough pressure to overcome any losses from the filter.

[Scopeman]

You have VIDA, so the fuel pressure is easy to check. You also need an external, mechanical fuel pressure gauge to connect to the fuel rail. I bought one from Harbor freight, worked fine.
In Vida, the fuel pump duty cycle, at idle, should be in the mid 30% range, and the external pressure gauge should be in the mid 40psig range.
when my FPS failed, the duty cycle was 55%, and the external gauge was 65psig. VIDA reported normal fuel pressure, because the FPS was bad.
You should also change the fuel filter first, easy to do.
I bought the FPS from NAPA locally. It is the Bosch part, but without the hole for the wire support fitting. IPD didn't have the part in stock, when mine failed.

[OslosisJones]

You have VIDA, so the fuel pressure is easy to check. You also need an external, mechanical fuel pressure gauge to connect to the fuel rail. I bought one from Harbor freight, worked fine.
In Vida, the fuel pump duty cycle, at idle, should be in the mid 30% range, and the external pressure gauge should be in the mid 40psig range.
when my FPS failed, the duty cycle was 55%, and the external gauge was 65psig. VIDA reported normal fuel pressure, because the FPS was bad.
You should also change the fuel filter first, easy to do.
I bought the FPS from NAPA locally. It is the Bosch part, but without the hole for the wire support fitting. IPD didn't have the part in stock, when mine failed.

Yeah, check engine light went on again yesterday, this time it was just the FPS code. Pulled the plug on the SMP sensor on Amazon (re-branded bosch w/o wire fitting, good reviews from many volvo owners), for about $60 which is not bad at all!

[OslosisJones]

New FPS seems to have cleared up my 'transmission issue', thank goodness.

Noticed an immediate improvement in throttle response and smoothness after changing FPS along with plugs and fuel filter.

Will be replacing lower transmission mount next weekend which will hopefully improve some of the vibration coming through the cabin.

Feeling a lot more comfortable with the car after doing some of these simple jobs. Getting ready to do the timing belt job if I ever get time on the weekend.

Still have a can of Trans Tune on order, will probably throw it the tranny just for good measure, and follow up with a Drain&Fill shortly thereafter. Should give me peace of mind for the next 20k miles.

[vtl]

Keep TransTune aside, better is the worst enemy of good. It would be wiser to d&f more often, every other oil change or even every oil change if you run oil for a long time. And install oil cooler and external filter.

Do you feel excessive vibration in P or N, especially on steering wheel? Yes -> rear engine mount.

[OslosisJones]

Keep TransTune aside, better is the worst enemy of good. It would be wiser to d&f more often, every other oil change or even every oil change if you run oil for a long time. And install oil cooler and external filter.

Do you feel excessive vibration in P or N, especially on steering wheel? Yes -> rear engine mount.

Vibrations comes through steering wheel and accelerator pedal, but not especially while in P or N. Instructions on replacing the lower transmission/torque mount are a little unclear, do I need to jack/support the transmission in order to replace the mount?

If lower mount isn't the problem I might have someone look over the other drive/suspension components (tie rods, drive shafts, springs seats, etc) to diagnose.

Might consider adding an inline filter, but the external cooler seems a little overkill. I don't intend to tow anything heavy or for extended periods. Is your rationale for holding off on Trans Tune the same as for avoing complete flushing (loosening too much gunk)?

[vtl]

Vibrations comes through steering wheel and accelerator pedal, but not especially while in P or N. Instructions on replacing the lower transmission/torque mount are a little unclear, do I need to jack/support the transmission in order to replace the mount?

No. Very easy, in fact. But I was talking about rear engine pad/mount - that one is difficult.

Is your rationale for holding off on Trans Tune the same as for avoing complete flushing (loosening too much gunk)?

Yes. All this gunk has to pass solenoids and tight passages in VB, where it will stuck for sure.

[kutcht1]

Glad you stayed with it and did not listen to the others that were saying "You need a new transmission". I install a trans cooler on every ATX vehicle I have ever had and have never heard of a ATX having issues with the fluid being to cold. A cheap tube and fin design cooler only drops it a few degrees but could make the difference in the end. The design of the XC70 leaves lots of room to add one so I ended up putting one of the large ones on. Cheap insurance, along with changing the fluid more often.
TomK