I installed a new set of O2 sensors because I was getting the infamous FF44 error. I cleared the error. Car drove until it reached operating temp, then threw the error again.

Searching the forum, I found a post that said to check the 12v power to the heater wire.

sure enough, I am only getting 0.4v, not 12.

I have cleaned the ground at the ECU, as well as the rear engine ground.

Fuel pump relay pin 87 is getting 12v.

I am tempted to temporarily wire switched voltage to the sensors to see if this stops the error.

What underhood circuit should I tap? And what should I check besides continuity between the ecu harness and the underhood heater connector for the O2 sensor

 

I may have my wires crossed. I am assuming the single wire with the spade connector is the heater. The other two wires that terminate in a Bosch EV1 connector are the signal and ground.

Or am I bass ackwards?

 

The single wire is the signal

The two in the Bosch connecter are for the heater

Cheers
DD

 

Thanks Doug. Ive just been researching this. Having black as signal threw me a bit.

 

Got me too on my first 02 sensor tests. No way I could have known,,, unless I asked... And me, like me, I didn't and I think it was Doug who straightened me out... It's all good. Live and learn

 

Doug has helped me out many a time here. I only get to the east coast once or twice a year to play with my cars. As the Jag has been laid up for 3 years after the accident, and is just now on the road, I am having all sorts of questions while I prep it for moving it to Seattle. Along with my 928 and my TVR.


Doug - Love to buy you a beer if you are anywhere around the Seattle / Olympic Peninsula area.

 

I hear that, Scott... I think if Doug, Grant or Greg were suddenly needing to handle all the beers owed,,, there could be trouble, but I hear ya! If not for (and all here) I would be in a very different place with my lil lady! Cheers all!

 

Hi Scottpeter

Before you wire up a temporary live have you checked the fuses in the boot on the rhs near the aerial? As assuming your car is a V12 the fuel pump 1 relay and O2 sensors are supplied by the same live feed. If this fails (as I discovered) the second fuel pump will kick in so the car keeps running as this has its own relay and power supply. Off the top of my head I think its a 10amp fuse in slot 9. If this is all good then it can only really be the relay that's failed, even If its clicking, this isn't necessarily a sign that it is fully functional.

Relay wise, I'm assuming it will be the same as my 94 XJS and the original part Bosch part no is 0332014112. This has been discontinued but Bosch part 0986AH0602 is a direct replacement. There are also other companies that make suitable replacements for not a lot of money too.

Good luck
Rob

 

Rob,

I was measuring the wrong wire. The color threw me at first.

But thanks for the info. A question: secondary fuel pump? Never heard of that.

 

Hi Scottpeterd

On the later cars with the in tank fuel pump, there are actually 2 pumps. The second pump under normal circumstances only switched on when the car is in excess of 2800 ish rpm and needs an increased flow rate so not to starve the engine of fuel. Quite a clever system for its time and as mentioned you can have a blow fused or failed primary pump and the secondary one will kick in with no interruption to the cars running under normal circumstances. When I got my car, it turned out the relay had failed but a previous owner had removed the engine warning light and my car didn't have the trip computer so for the best part of 3 years I had no idea it was running on the secondary pump only!

Going back to your initial query, have you managed to get rid of the FF44 code now?

Thanks
Rob

 

Rob,

where is the second pump located? After sitting in the frame shop for 2 1/2 years, there was no fuel pump action, so I pulled apart the boot to check circuits. Turned out the fuel pump relay was bad, so I replaced that. Seems to be a common problem with my S600 and 928 as well. They all sit too long between drives.

i have NOT solved the FF44 issue.

Plug wires were replaced 200 miles ago. Recently tested them, and they were fine. All the plugs on the A bank pulled and inspected. They are firing fine.

All electrical connectors to the injectors removed, cleaned and reinstalled. This winter, I taking wire and new connectors back with me to Uganda to build a new harness.

The harness to the ECM in the boot has been removed, cleaned and de-oxed. The ground there has also been cleaned.

i have put a stethoscope to the injectors while the engine is running, and they all “click” uniformly.

i have replaced the A bank temp sensor that is responsible for the 26cu, just in case.

The 02 sensors are giving out voltages in the expected ranges, as measured by the test connector in the boot.

The 6 pin connector going to the ECM resistor pack has been pulled and cleaned. All grounds have been removed, cleaned and de-oxed

Two remaining things. The intermediate pipe is leaking at the connection to the RH cat, so Im replacing that tomorrow. Both cats were gutted, after finding the RH cremated by the infamous Marelli fire.

I am going on the assumption that the FF44 is caused by too much oxygen in as measured by the O2 sensor. I have not been able to track down a full explanation of what mechanism actually fires this condition,

I am running out out of ideas here

 

And yes, even though its for the later MYs, I have followed the suggestion in the TSB...

 

Hi Scottpeterd

First thing we probably need to do is determine your exact model type. As mentioned I've been making a few assumptions. I have assumed that its an early facelift coupe (smoked tail lights but rubber bumper and 5.3ltr V12)? If that is the case, then the fuel tank should look vaguely like this one. https://parts.jaguarlandroverclassic.../brand/jaguar/ If at this point I'm still on the right tracks, item 2 on the diagram is the housing that holds 2nr fuel pumps for the car.

If however you have the earlier pre-facelift type, this has an external swirl pot and pump (singular), then the information provided will likely be of little help to you.

Assuming I'm correct up to this point, It is unusual for the pumps to fail so I would be scrutinising all the other components first to make absolutely sure nothing else could be causing your problem. As mentioned there is a shared fuse for both the fuel pump 1 and O2 heating circuit. This would be the first thing I'd check as you just need a meter and to remove one piece of boot trim to test.

Second thing would be to check the O2 sensors as it wouldn't be the first time I'd brought a brand new item to find that it was actually faulty. A good working O2 sensor should be reading between 0.1 - 0.9 volts with around 0.45 being at good idle. It should also not fluctuate erratically especially when warm from one second to the next. PLEASE NOTE this is checking the reading from the sensor, not the supply voltage to the sensor. To test these I would be connecting a meter to the sensor using the connection in the engine bay as this will give a true reflection of what the sensor is reading. This can be done without having to disconnect it from the car (probes can be pushed into the back of the connector). Also to note here the FF44 code refers specifically to the right hand bank O2 sensor I believe. So make sure its that one you test or test first!

The other thing we haven't considered yet is that the car might be performing correctly and there is an issue with the fuelling mix or a leak in the system that could be upsetting the sensors. Although like the fuel pump, this is unlikely having carried out all the works you've listed above.

Lastly I must state that I am by no means an expert on this and can only go by the experience I've had with my 1994 V12. I'm sure there will be differences between the cars but the general principles should be the same.

Best of luck and keep up posted on your progress
Rob

 

Rob,

yep, my car is what you have described. Is the second pump contained within the housing for the first? On my S600 they are side by side, for increased volume at high speeds.

Im am getting what should be good reading from the O2 sensors (at the connector under the bonnet and in the boot), . 0.4 to 0.6 volts. Consistent from between the banks. And Ive measured the expected 3 amps on each bank in the heating circuits (measured under the bonnet).

iI have to assume that it is not the O2 sensors causing the ECM to throw the FF44. I can detect a very slight misfire at idle. Ihave replaced the distributor cap, rotor, wires and plugs about 200 miles ago.

A misfire will cause more oxygen to be detected at the O2 sensor. But the duty cycle of the fluctuations is to short in duration for a VOM to capture them. And I dont have a scope here.

I also find it difficult where to go next. If it is truly a mis fire that Im hearing, that has to be spark related. I am hesitant to buy new plug and wires so soon. The i side of the dizzy cap looks fine, with no arcing or carbon tracks.

 

Hi Scottpeterd

Yes the pumps are side by side within the housing as per your description of the S600.

If your getting good O2 sensor readings that's a good start however, if the heating circuit to the O2 sensors are not operating, you will still get the FF44 error code. This is where the fuse in the boot comes into play as this is the only power source to the heater element within the sensors.

There are a lot of things that can cause a misfire, including the fuel pressure regulator not operating correctly but as this misfire has been described as slight, I don't think this will be the problem causing your FF44 code. My XJS also has a slight misfire (especially noticeable at idle) but does not cause an FF44 code.

Could you let me know if you've managed to find the fuse in the boot and check it so we can rule that out as the problem?

Thanks
Rob

 

Hi Scott

Just as I posted my last comments I found a fuel tank with pump for sale on the UK eBay site.

https://www.ebay.co.uk/itm/Jaguar-V1...temCondition=4

Pictures 3 & 5 show the two pumps for reference.

Thanks
Rob

 

Hi Scott

I have found a electrical wiring guide for your car I think (http://www.jagrepair.com/images/Elec...electrical.pdf) and its quite interesting. If I'm reading this correctly then you perhaps do not have the inline fuse like I have. This also suggests that your car might only have a single fuel pump as well.

But looking at this you should be getting 12v at the Blue/Red wire going into you O2 sensors when the car is running. Again if we can confirm this then we know that the O2 sensors are definitely working as designed and move onto the next part of the diagnosis.

Regards
Rob

 

Rob,

The sensors are getting 12v. I was able to measure that early on.

Attached is the EFI section of the wiring diagram. There are no fuses for either the ECM or the sensors.

 

Hi Scott

Thanks for clarifying. This is going to be beyond my experience as, as mentioned mine is a 94 model and evidently differs more then I had assumed. However, on the 94's (and possibly earlier cars) Jaguar did issue a TSB regarding FF44 codes being caused by poor grounding. There recommendation was to install two additional grounds. One in the engine bay to the bulkhead and one in the boot I think (going by memory here). So may be worth looking into additional earths in case this is causing spurious readings.

After that I can only suggest testing;

1. All contacts within the engine management system.
2.The exhaust for leaks, as mentioned it may be a fuel mix imbalance and rectifying this could clear thge FF44 code
3. Fuel pressure regulator. To do this you will need to find out what pressure the rail should have. Again on the 94 its about 3 bar but earlier cars were less and I don't know what pressure your car will require. I also think this is unlikely to be causing your FF44 error but happy to be proven wrong.
4. Fuel filter. If gunked up a bit this may affect the supply and case an fuel/air imbalance

Lastly perhaps someone who has an identical car and previously suffered from the same issue might be able to provide some more useful information.

Sorry I can't be more helpful but do keep us updated on your progress!

Good luck
Rob

 

I have a '92, and also had the FF44 error. It took a lot of work to track down the problem, as while the O2 sensor was initially replaced, the error soon came back. All sorts of things were tried, including the extra earths, but what turned out to cure it was getting a genuine Bosch one--the fluctuations moved as required, but not enough/fast enough and triggered FF44. They have to move X amount within 450 revs, or something like that.

More details in this final post HERE, and you may want to read the entire thread, as it's full of good advice that I got given.

Oh, and I don't know about fuel pumps being reliable. I've had to replace mine twice in two years. And I'm fairly sure the '92s don't have a secondary one, as when my pump failed, the car simply would not start.