hi all,
Jaguar XJR 4.0SC 2001
i thought i had maybe solved this, but i am quite at a dead end now, hope you can help or give some pointers..
One evening my sierra needed towing about 10 yards on my drive as her battery was flat and needed to move to a safer position.
The drive is flat. i hooked up a tow-rope on both towing eyes, and very tentatively eased the throttle forward in D. i hesitated once just to reposition the sierra's wheels and the XJ was in neutral. (i didn't put her in P as i thought i might have strained the 'box) all was well, and i towed another 5 yards and put XJ in N whilst removing the tow rope. Then i proceeded to drive off and hesitated at the end of the drive, and i saw "Failsafe Engine Mode" come up. it was strange, as i hadn't forced or jolted whilst towing.
The next few days i have done the following:
1. bought a new scanner (Autophix OM 126P) which incidentally, was rubbish as it only worked once then just says "FAIL" when it wants to read the port (big waste of £59.99)
2. the codes P1111 (Intake air temp sensor circuit intermittent high voltage) and P0507 (idle control system RPM higher than expected).
3. Bought and fitted a new MAF
4. Checked for any loose pipes like PCV
5. cleaned the butterfly as far as i could, with intake cleaner -it wasn't really dirty anyway
6. checked the TPS was secure
7. checked the throttle cable wasn't unduly slack or tight
8. checked all fuses under bonnet, boot, and N/S rear fusebox, all ok
9. did hard resets many times
10. took her on a 2 mile run, no clearance of Engine Failsafe mode.
11. did all of this with a 100% charged battery, 12.84V and all terminals clean and tight.

After each reset, Engine failsafe mode comes on immediately (even with ignition on but no running of the engine) and sticks the revs at 1200 after blipping initially at 2500. it is about double what it used to be.

The TPS is fairly new, only 7,000 miles ago.

it's a tad annoying , but as i have lost the will to live with the scanner, as it will not now read, i am reluctant to buy another....




cheers

 

The Autophix models are particularly susceptible to failure if you plug them in or unplug
then with the engine running. They are generally good scanning tools.

 

That scanner is useless. P0507 - it's telling you what you already know; P1111 - it's giving you wrong info. From Jaguar DTC Summaries:

P0507:
Intake air leak between MAFS and throttle
Intake air leak between throttle and engine
Engine breather leak
Throttle valve stuck open
Throttle assembly failure

P1111
System checks complete since last memory clear
If it is flagged after DTCs have been cleared, it means that all FIVE (5) engine management OBD diagnostic monitor drive cycles HAVE BEEN COMPLETED.

 

Years ago I wrote a post called "YOU cannot clear a P1000".


YOU cannot clear a P1000.
The readiness monitor will change that to a P1111 when all are complete.

Either DTC P1000 or P1111 will always be present in the ECM!!

P1000 circle of insanity

The P1000 code is present when the ECM has had all DTCs ‘cleared’ from the non volatile memory or the battery power to the ECM is interupted.

The P1000 is changed to P1111 when the readiness monitors are completed by a specific ‘drive-cycle'.

People often see the P1000 DTC and try to clear it. This resets the DTC to P1000. (again)

Then the car is driven until the monitors change the DTC to P1111. (some guides reference this as a fault with the intake air temp sensor)

Jaguar P1111 is just the ECM ‘being-happy’, not a fault.



People see the P1111 and decide it must be a fault and clear the DTC.

The ECM now defaults to P1000 and the circle of insanity continues.

Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.
Then the car is driven until the monitors change the DTC to P1111.
The code is cleared and it reverts to P1000.

 

ah I see - thanks! So I may have replaced the MAF for nothing? Should I just put the old MAF back on and see what happens?
also, do you think I should adjust the throttle cable?
cheers

 

I would first check the voltage on the battery terminals while the engine is running to verify operation of the alternator.

 

yep i did that as i say , the voltage was 12.84V and 100% on the charger... i am at a loss why i just cannot get the revs down....

 

Not the battery voltage after it was charged by the charger, "the voltage on the battery terminals while the engine is running to verify operation of the alternator".

 

ah yes - sorry, 14.4 volts i think - and the alternator is new - 5,000 miles ago so no issues there.....

 

The TPS sounds like it needs adjusted. Whenever I’ve messed with swapping them out, I’ve found that I needed to adjust them to bring the RPM’s down more than anything.

 

Hi addicted2boost
thank you so much.

I opened butterfly carefully, I thought I’d maybe not cleaned the butterfly enough. So as I could still see residue I totally sprayed carb cleaner around it and worked it with an old toothbrush. Then sprayed again.

I then undid the TPS top screw (if anyone knows what these sizes and threads/heads exactly are, kindly let me know as I couldn’t find a nice fitting torx) I couldn’t seem to undo or access properly the bottom screw but I managed to lever it anti-clockwise by a couple of degrees. Did back up.

Then I sprayed through the crankcase breather pipe that’s attached to the air intake whilst the whole thing was off. I then sprayed electrical cleaner in the MAF plug and cleaned with a toothbrush.

So after reassembly I started her up….. “engine failsafe mode” immediately. I then turned off…did a hard reset of the ECU by putting the Negative lead on to the positive terminal, for 30 sec. Then leads back on.
Waited for 2mins. Then turned key to ignition on but not start her. Leave 2 mins. Started her up.
Revs 2500 then dropped from the previous 1250 to 900. I let her get warm, and low and behold the revs dropped to 750 but still EML but when she reached optimal temp, all of a sudden “engine failsafe mode” disappeared!
I then took her on a 3 mile run and all was fine. In fact she seemed more positive in response.

Now I’m not sure what I did, but my instinct tends to point to a sticky butterfly. Maybe on towing, the revs didn’t quite match the ECU memory and maybe forced the butterfly in its gunge, or tricked the TPS. Or maybe it was a coincidence that night, the MAF decided to give up - I’ll never know, but the sticky butterfly or TPS being tricked is my bet.

Cleaning the butterfly with toothbrush and carb cleaner

After initial start up

When she got to optimum temperature


I would just like to thank you for your responses and wish you a great weekend!

 

I’m willing to bet with what you mentioned about the tps reporting back and the revs didn’t match makes perfect sense. I don’t think I would’ve thought about that one. The tps reporting back to the ECM (among other sensors), the wheel speed sensors reporting to the ABS module and the transmission reporting back to the TCM all probably agreed that something is wrong here. The fact that you were towing (even the short distance) with a car that was never meant to tow such a heavy load (truck) that it probably just wasn’t happy.

 

Yep thanks.. apologies, I forgot to say, it was only a Ford Sierra XR4x4 2.9 not a big US truck… I’m in the UK so she’s less heavy than the XJ