Hi everyone,

I just picked up my 1995 XJ6 from my folks. It was my grandparent's car, then my parent's and now mine. Whoohoo!

So I drove her about 500 miles to take her home. I doubt this car has seen any highway driving in at least 10 years. It was a really pleasurable ride (with the exception of the crackly speakers which are on my fix list now).

However about 300 miles into the drive I got a check engine light, though it was still driving fine. Today I had Autozone read the OBD for me and got the following:

P0420 Catalyst system efficiency below threshold (Bank 1)
P0430 Catalyst system efficiency below threshold (Bank 2)
P1177 Long term fuel trim Too rich- Banks 1 and 2 (FMFR)

I'm a total newbie to this car and I'm in the process of reading up on these systems, but if anyone has any immediate thoughts on likely culprits with these codes coming up together, I would love to hear your input.


Thanks in advance!

 

On the back of the engine block valve cover to the left there are 3 connectors pointing up . One is a grounding wire connector and the other 2 are the aft O2 sensors which give you the 420 and 430 . Look for green corrosion on those 2 connectors and clean up with some baking soda and water then spray with some oil . Keep track of connector hookup position as they will get mixed up .The 95 is a little different in some aspects so here is the 95 Electrical Guide , look at the upper right on page 51 .

On the AJ16 engine the #1 cylinder is the forward most position ( opposite of the AJ6 ? ) . So the B1S1 ( bank 1 sensor 1 ) is on that pipe forward of the forward Cat . On the ECU side of the connectors they have the same wire colors with exception of the one important return signal wire to the ECU . B1S1 Green , B2S1 Brown , B1S2 Blue , B2S2 Red . Best to follow with hands and eyes to the installed pipe position . Look for some corrosion of the B1S2 and B2S2 connectors behind the back of the valve cover .

http://www.jagrepair.com/images/Auto.../jagxj1995.pdf

Clear the codes and the long term fuel trim may relearn itself in the ECU as the battery may have been disconnected causing this lose of this learned parameter

Editing

 

What Lady P. said and also running some fuel injector in your gas tank may not be a bad idea.

I have had the P0420 code in both of my XJ6s. I may eventually need O2 sensors and or a new cat. convertor.

 

Cheaper connector ready sensors for X300 if it comes to that

 

Ok, I think I understand how to identify the connectors. Thanks, Lady P. for all of that! It's pouring rain right now but I will have a look when it clears up a little.

And Scotlad, I had thought about injector cleaner-- mostly because the nice guy at AutoZone read my OBD in the rain and then I didn't really have anything to buy from him.

While I'm sorting this out, is there any chance I will harm anything by driving it?

 

No , enjoy . Did you download the music ?

There was some discussion on putting on a additional 12 mm spark plug physical spacer and or resisters on the aft sensors to bias the readings to rid the 420 , 430 before changing or reconditioning the cats

 

I would have loved to listen to some beautiful classical music on the drive. I even picked up one of those cassette to iphone things. But the speakers crackle and pop so bad it was unbearable. My next task today is to look up that repair.

That picture is VERY helpful!

Oh, and also, when you mentioned before about getting looks in the jag, I didn't quite understand what you meant.... I can't believe how many people I see checking out my ride... and maybe it's my imagination, but I felt like other drivers on the interstate were much more polite than I'm used to.

 

......You're driving a legend , they're the long looks until you pass out of veiw , been there , done that

Speaker Repair :

https://www.jaguarforums.com/forum/x...woofer-189654/

 

If the car has been sitting long, giving it a blast (Italian tuning) might shake up the car. However, given the age (and mileage?) of the car, maybe it is time to replace the O2 sensors and front cats altogether rather than a temporary fix as this is part of preventive maintenance to improve fuel efficiency and air quality for all.

 

I've got a 96 that gives an occasional P030/P040, I just clear 'em and move on. Have had two occurrences thus far...maybe 3-4 mo. apart.

Someone here on the forums recommended BG Products B44K for fuel injector cleaner. I ran a can through each rolling stock on the premises. It resolved a recurring niggle on one of the 3.0L S-types.
I'm a believer. Only available from certain service facilities, rather than over-the-counter at auto-store chains. But of course, there's always Amazon:
Slightly cheaper by the 4-pack if you are doing multiples.

 

The car wasn't exactly just sitting, but has only been driven occasional short distances in town for many years. I'm curious about the idea that the ECU might need to relearn the trim info. I had a RAV4 on which I had the ECU resoldered and it took some time for it to relearn when to shift the transmission. Admittedly, though, much of this is overmy head.

if it turns out I need to replace O2 sensors I certainly will. But I wonder, is it likely that both would go at the exact same time?

 

Will give this a try.

 

As I understand it ( this is my first Jaguar ) is there are 2 fuel trims ( of fuel /air mixture ) called long and short . The long is a in the ball park value that is learned and stored and the short is a refined real time value calculated by the ECU from inputs from the following engine regulation sensors :

O2 sensors
Throttle position sensor
Mass Air Flow sensor
Engine Coolant Temp sensor ( cold weather assist by making it rich )
Engine Inlet Air Temp sensor
Manifold Air Pressure sensor ( not on the X300 )

In order for the long term fuel trim to be learned the engine must satisfy or hit certain targets such as RPM's , Time , Cycles , etc .
Not to be confused with error code inhibits which keep them from showing until a certain cycle count . The O2 sensors are inhibited by design until this count is satisfied otherwise you would be coding intermittent nuisance faults as this system can be fickle . This notion of non - instantaneous results after you have done something can throw you off as you troubleshoot something , you have to let it play out .

Both sensors physically completely failing or going out of range at the same time is very unlikely and the problem may be in a common denominator like the shared reference voltage power source from the ECU . So we'll look at the wiring first .

One thing to keep in mind is the X300 O2 sensors are titanium based sensors that generate a resistance that the 1 reference voltage shared pin is modified before returning back to the 4 individual ECU input pins . The more common O2 sensors are zirconium based which generate their own voltage from a ground point to the 4 individual ECU pins .

https://www.ngk.de/en/products-techn...lambda-sensor/

Pin Red 8 on the ECU is the area of interest and is wrong on the Jaguar Wiring Schematic breakout sheet of values on the page before the print as it is actually a voltage but what you are looking for is corrosion on the sockets and pins and the 2 tabs on the sockets are gripping the pin . Look also at the feedback return input pins 6 ,16 , 18 , and 20

Look also at the O2 sensors feedback input wire shielding grounds along the upper engine firewall/ bulkhead as it is a very fickle intelligence signal .

One way to know if your fuel trims are off is to look at the gas mileage value on your dash as there is a button on the right side fwd of steering column that will display the gas mileage .

Now back to what is really important is that stereo . Before you fix the speakers the cassette input adapters result in a distorted sound as they are lousy . better to soldier in a hardwire input jack inside the unit