Clearing memorized fault codes

[Jaguar5993]

Hello,
I might be wrong, but I could not find anything in this Forum about clearing old memorised fault codes.
I had a FF14 (coolant sensor etc.) fault come up a few years ago and repaired it the old fashioned way by 'trail and error' replacement, rather than paying a garage to find and clear the code.
I’ve just left it displaying,as the car ran great.
I have known for sometime now, that by having the battery disconnected, that this does not clear any memorised codes.
Does anyone know if there is a DIY method of resetting this?
My car has the old OBD-1 /PDU /JDS set-up (think it went OBD-2 from MY1995.25),so I was wondering if there is a laptop/software program out there today, (you know the ones, from eBay China) to do this myself ,if you can still get the OBD-1 connector etc. (?)

I guess there is the possibility that the FF14 is still genuinely there, even with a new sensor, as there might be a fault in the wiring!
As I said before,the engine was running well.
Due to starting the resto now, my car is now on a SORN and the insurance cancelled, so its not urgent yet....I like a bit of forward planning
Hey! I can always re-install the 1970's clock instead of the trip computer
All the best,

[Jaguar5993]

I did a little bit more digging around on the internet.
I came across this....(it seems a safe link)

https://www.obdadvisor.com/difference-o ... -scanners/

Basically it says, you can use a joint ODB1/2 scanner (one on eBay and yes, made in China £74) but you just need an ODB 1 port connecter.
What I am still not sure about is if you can only use it to find fault codes, just like the Jag trip computer does, but can you actually clear/reset the codes with it(?)
Is the only option I have, is to use a Jaguar PDU (costs a lot of money to buy) with a garage/specialist etc?
Still looking.

[Jaguar5993]

Honestly, I don't mean to answer my own queries all the time (just looked at some of my past posts)
I should really do the research before I post...sometimes, hah!
I found this interesting text from the well known, Kirby 'Experience in a Book'.

"CLEARING FAULT CODES -- 6-CYL: Gary Penovich says, “On a ‘94, you can clear the fault code from the ECU
without disconnecting the battery. It's a piece of cake. Open the dash trim panel that's underneath the passenger airbag
by pulling down on it. Unscrew the passenger heater vent cover. Remove the small trim panel from around the heater
vent. You should see a purple connector attached to a yellow(?) wire. The connector has only one conductor in it, and
it isn't connected to anything. Short that conductor to ground for 3 seconds. It will clear the fault code. The process
may be the same for all AJ6 powered XJS, perhaps AJ16 as well.
“I have actually moved the connector outside of the trim by running the wire through the vent cover. Now, I can access
it simply by swinging the dash panel downward. It comes in handy after disconnecting sensors while the engine is
running. The ECU will flag a fault even if the key is on with the engine off! "

Ok ,it says for a 6 cylinder engine, so not too sure about the V12(?)
I guess there will be many not willing to take a risk and go this way, but knowing me, I probably would.
I hope this will help .
Anyway, what a great book that is.

[Andy P]

Hi nicholas6885,
I've read about that wire on other Jaguar Forums so it could be worth a try.
Let us know how you get on.
I've just found the Kirby 'Experience in a Book' in PDF on the internet so if anyone would like it here's the link:

https://drive.google.com/file/d/1U5g2DH ... sp=sharing

Over 700 pages of information so should keep me busy for a good while.
Good luck with restoration and stay safe.
Andy

[ptjs1]

Hi Nick,

Apols for coming in late I've just seen this thread. A couple of thoughts:

I'm not sure you can use a generic OBDII scanner with a Jaguar PDU interface to interrogate your car. I haven't seen an OBDII to Jaguar PDU interface plug before anyway.

As regards the shorting plug behind the panel, I've read on a number of forum that this should work on your car.

Let us know how you get on!

Good luck

Paul

[Jaguar5993]

Thanks Paul,
I had a feeling that would be the Achilles’heel,as I haven’t heard of that connection lead before and it would of been done by now(?)
I will try the short circuit ecu reset, as mentioned.
I will not be going anywhere with the car and I can do it before I start stripping the car down.
I will try and take some pics of the process.I might try and generate another little fault to verify.
Cheers!

[Jaguar5993]

Hello again,
With reference to my post in trying to clear a memorised FF14 code and using the info on the various websites, this is what I found after I took all the relevant bits apart.
No purple connector with a single yellow wire (some say yellow and green) .
In case there was a LHD/RHD mix-up, I took the drivers side apart to make sure. Also, I took out the trip computer and the radio to see if it was behind that...no,no and no
There was this larger red/mauve connecter with a Y/G wire amongst many others (pic), rather than the stated purple one with a single Y/G wire.
Could it be that as my car is a 1994.75 V12 6.0 model, Jaguar changed it??

Oh well....'nothing ventured, nothing gained'.

Unless anyone else knows any other routes to try.
Cheers

[ptjs1]

Nick,

Even though you have a 1994.75 car, you are saying that you don't have an OBDII connector, you have a PDU one in the boot?

My understanding is that for pre-OBDII vehicles, resetting of fault codes could be achieved in 4 ways:

- Earthing the "hidden" wire
- Disconnecting the ECM plug
- Removing the ECM fuse
- Disconnecting the battery

Personally, if I was disconnecting the ECM I would disconnect the battery first, which somewhat obviates the need to disconnect the ECM!

Just because I'm intrigued, I'm going to check my 1994.75 OBDII car tomorrow and see if I can find the hidden wire!

I'll let you know!

Paul

[Jaguar5993]

Hi Paul,
This is all very interesting.
I wish that purple connector was there.
I remember a Jag specialist friend 16 years ago said mine was not ODB11 and the older JDU connector is located at the bonnet release handle in passenger footwell.
I had always known my car was manufactured in June,early July 1994.This was confirmed by that piece of trim I removed having 06/1994 written on it.It was registered in Aug 1995!
I believe this was not unusual.
I only thought it was the 1995.25 model (probably manufactured in November 1994) had the ODB 11 and a different brake servo etc.
Thanks for your info.
I will now try ECM plug and battery off method.
I guess we are dealing with mid-automotive progression with electrics...swinging between old and newer tech.All good fun
Already missing driving it.
Cheers

[ptjs1]

Nick,

If you've got the connector by the bonnet release, then I THINK its the OBDIi-style connector. It would make sense as the 1994.75 AJ16 cars have the same plug there so I suspect Jaguar standardised wiring etc.

Take a photo and well confirm. The old PDU connector was originally in the boot. I also THINK the 1994.75 v12 isn't fully OBDII- compliant but sufficient to allow for engine ECM code recognition etc

If so, you're laughing as a cheap £5 dongle and £2 Bluetooth software is your answer!

Paul

[Jaguar5993]

Hi Paul and others,
Had a very interesting morning investigating all this.
Firstly, I was getting bogged down with all the abbreviations, so I can only relate to the late 6 litre coupe's and hopefully the same with your AJ6 4.0 engine cars.
Thanks for your last post.

So is a PDU (Power Distribution Unit) used in the older cars and the reading port is in the rear boot/trunk and then read by a JDS (Jaguar Diagnostic System.) tool?

Ref: to my first picture... Do you think it looks like my 1994.75 has an ODB 1 (On board Diagnostic System) port and is normally read by a JDS tool also and that would of reset the MIL (Malfunction Indicator lamp) codes, or sometimes called DTC (Diagnostic Trouble Codes ?)

I read that most of the engine faults that show in the trip computer come via the PCMF (Powertrain Control Module Fuel) that is at the rear right ,in the boot.
Is this what you call the ECM /ECU(Electrical Control Module/Unit)?

If I bought one of those joint ODB 1 & 2 scanners, with that port shown, I should be ok?
Not too sure what else I would need and how your suggested Dongle and Bluetooth set-up would work.
Sorry about all the questions.

Now...I got a good result with clearing that FF14 fault and it was far easier than I could ever imagine.

Battery not disconnected.
Ignition 'off'.
RHD car, take passenger fuse cover/panel down and take out fuse...No.14 ,5A P.I. MEMORY (you did suggest a fuse removal ,so I guess that's it.)
Ignition 'on' for a few seconds (nothing displayed in Trip Computer)
Ignition back 'off'
Put that 5A back.
Ignition back 'on' and the fault code should not be there.

I pulled off LH air filter sensor and got FF16 and then tested this method again and it cleared it again.

'Quiz of the week'.....Does anyone know what this little, yellow connector is for near passenger bulkhead?
(see last pic)
Someone from 1995 to 2001 had cut a slit in the sound proofing to expose this two wire lone connector .The green/pink dot wire goes in to the PCMI (Powertrain Control Module Ignition) and the black/green dot wire goes in to the Abyss

Thank you again for all your help and its nice to have something to do with our time these days.
Best wishes

[ptjs1]

Nick,

I'm down with my car now. I've removed the cheek panel and I can't find that reset wire. It may be under the centre console but I can't be bothered to rip that out right now!

The good news is that the socket you've got IS an OBDII-style connector! So I think that confirms my theory that, whilst not fully OBDII- compliant, the 1994.75 v12 can probably have its engine ecu read by a standard OBDII plug and software!

So get yourself a cheap Bluetooth or wireless dongle and a software app. If you use an Android device the Torque Pro App is very good for about £3. I use it all the time.

Good luck

Paul

[Jaguar5993]

Hi Paul,
Just a little update and the result of my experiment with an OBD scanner.
As you said, I have the ODB II style port ,so came up with a great combination of an iPhone app called 'OBD Fusion' and a Bluetooth port by Veepeak 4.0 LE.
I found out that to use your iPhone app well , it really needs to be Bluetooth 4.0 Low Energy (LE) or I believe 4.0 or 2.0 might work.

I set it up correctly and indeed, the Veepeak and app software spoke well together, unfortunately my 1994.75 V12 ECU was not speaking to them...
I also uploaded for free, the OBD reader ELM327 to test again.

I guess some professional garage folks might of said " I could of told you that."
I tried both of these software's on my 2004 Honda Accord 2.2CDTi hack and they all worked well (even found a new fault on that car.)

I am glad I got the Veepeak and it didn't cost that much (£9.99 app and £34 for the Veepeak) and I can use it on all of the families normal modern cars as well.

Just found this on Jag-lovers forum...

"My 1995 V12 has an OBD II port, but my generic OBD II scan tool won’t read anything when connected. My understanding is that Jaguar started using the OBD II connector as mandated, but my opinion is since the V12 was being phased out they probably only invested enough man-hours so as to enable the OBD II connector to interface with the JDS tools"

So there it is and in conclusion;
XJS 6 litre MY1993.25 to 1994.75,even with an OBD II port will not work with a non JDS setup.
As you already told me, your 1994 AJ16 4.0 will work (think they sold more AJ16's to the U.S.)
Probably the very last 1995.25 (new servo type) 6 litre V12's would be able to be OBD II scanned like yours(?)
Just hope this might help others.
Now back to the trip computer and removing that 5A P.I Memory fuse to clear faults.
Thanks for your help.
Cheers

[ptjs1]

Nick,

That's disappointing but not entirely unexpected. Forgive me questioning it but I assume you tried it with different approaches eg ign off, connect obdii plugin, turn ignition to Pos II, or else turn ignition to Pos II, then connect obdii plugin etc? I guess it's possible but it seems strange that Jaguar would apparently have had to issue OBDII port to PDU interface plugs to every Jaguar dealer to handle these 6 litre cars with OBDII ports? If not, I'm confused as to how Jaguar dealers worked on 6 litre XJSs when they were new?!

If I were you, I would contact a variety of Jaguar independents such as our own David Marks, Ken Jenkins, Keith Parrington and perhaps Ray at Surrey Jag Centre, Chris Knowles at KWE, Swallows Jaguar in Bristol and Clarkes of Sussex and ask them all exactly what they would do to interrogate a 1994.75 MY 6 litre that has the physical connection of an OBDII-style port and what software package they use. They must all have had to do this as some time! Clarkes, in particular have imported a number of 6 litre XJSs from the US that are US 1995MY, which equates to RoW 1994.75 MY. There's also a part of me which would be surprised if Jaguar changed the software setup on 1995.25 and 1996 MY 6 litre models.

Although they often work well, OBDII Bluetooth plugins can be a bit hit and miss. I had a cheap one that was forever playing up and I threw it away and replaced it eventually. You might also try a few more OBDII software versions. (there's plenty of free / trial ones available just to try and see if you can get anything to work).

Cheers

Paul

[Jaguar5993]

Hi Paul,
What a simple idea....call the main Jag players and hear what they do.
I followed the instructions.I was prompted along.
I had read that for such a short distance the Bluetooth 4.0 is good with a iPhone 12 mini that I have.
The 2 apps I tried worked really quickly on my other car(2004).
Seem to remember the Jag repairer I knew 19 years ago had a job in his workshop to find a lead.
It was a JDS tool lead with our OBD connection on the end.
I’m sure he said the 1996 models had OBD II (?)
For me,I have the right apps ,but the ECU was limited to who it speaks to.
Fortunately ,this is not serious.I have always liked working on my own car, as it’s only just before the period where it has ruled out the diy machanic .

Cheers