How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Richard Your Own Question
Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 15508
Experience:  12 years at a Ford/Lincoln Mercury and Jaguar dealer as technician and shop foreman.
Type Your Jaguar Question Here...
Richard is online now
A new question is answered every 9 seconds

04 XJR P0172 P0175, fuel pressure (scan tool) 54psi idle

Customer Question

Hey Richard, 04 XJR P0172 P0175, fuel pressure (scan tool) 54psi idle jumps to 69 wot. (high?) No back pressure in cats but both rear o2's reading low at .001+/- changed both. Can't get V reading front sensors from 4 different professional scan tools. Equiv right around 1000 both fronts, measured in Ma only what is target for these please?
Mode 6
1d max 36606 measured 33256
1c max 36606 measured 33281
1e min 28930 measured 33281
1f min 28930 measured 33256
which component(s) is this for please can't find it anywhere. Vacuum gauge shows normal. air filter out no change, replaced MAS looks normal. Coolant temp (scantool) normal, Gas mileage in toilet. Customer drives 1 mile to and from work daily :(
Rich codes came on twice on freeway adaptive cruise on, right when it took over on braking and decel. (coincidence)?
Checked fuses for cats, OK
No missfire codes
I have no hair left......
Submitted: 9 months ago.
Category: Jaguar
Expert:  Richard replied 9 months ago.
Those front oxygen sensors read in amperage since they are air/fuel ratio sensors. Fuel pressure looks good for supercharged engines. We may have an issue with the mass air floor sensor connector pins. The ECM will default to full rich if it loses signal and in some cases will not store an actual mass air flow sensor code. We also need to check the fuel trims as they are most likely in the negative. Disconnect the negative battery terminal cable to reset the fueling adaptions and they should reset to zero. See what the trims go to after a good road test. Let me know.
Customer: replied 9 months ago.

OK will do. Cheers.

Customer: replied 9 months ago.

Still same issue, codes.

Customer: replied 9 months ago.

P 0101, cleaned and bent connector pins testerday

Expert:  Richard replied 9 months ago.

That is the only code stored?

Customer: replied 9 months ago.

P0172 p0175

Expert:  Richard replied 9 months ago.

Were you able to read the long and short term fuel trim percentages?

Customer: replied 9 months ago.

yes and after cleared codes yesterday, within 1 minute of driving from cold open loop both rich codes came back. I wouldn't have expected that in warm up phase.

at idle closed loop:

St B1 & B2 -.2.3 to 0 +.8 but mostly 0

LT B1 -8. to -.5

LT B2 -10.2 to -.6

Freeway steady:

ST B1 0 to -.6

ST B2 0 to .45

LT B1&2 -18 to -23

Customer: replied 9 months ago.

Finding that P0103 comes up first in pending, changed to another MAS from other car same issue, going to do pinpoint tests to check wiring to ECM etc. will advise.

Expert:  Richard replied 9 months ago.

Let me know how the testing went. It does sound like there may be a problem with that signal wire.

Customer: replied 9 months ago.

Hey Richard, thanks for checking in. After running pinpoints for p0103, and exhaustive continuity on the ecm harness and sensors which all pointed to the maf being bad I swapped it out for the 4th time and it fixed the problem, I have yanked the harnesses and connectors and no change so I think it's ok. Long and short trims are perfect. 4 sensors later......... just goes to show u. Denso and straight from Jag bad out of the box. Put a used one I had upstairs and bingo.