2005 S-Type 3.0 120K.

I have been struggling over the years with a P1646, 1647 that would ONLY occur at idle and ONLY in the summer during high heat days in Dallas. Most of the time, I wold be driving on the expressway and then come to idle at a stop light for a couple of minutes and I guess that was generating the higher heat. This has never occurred when I am actually driving the car and only at idle. Most of the year- zero problems. NBCAT was good enough to suggest that I must have some resistance in one of the circuits and that will higher heat the resistance goes up. That makes good and common sense. Usually it I got a code with CEL, the next morning I could go drive the car around, make several stops and usually on about the third or forth stop the CEL goes away. If I have a pending code, it would go away when I turned the car on in the morning.

Now out of the blue in the last week I am getting code P2096 and P2098 on top of and apparently before the P1646 and P1647, which are circuit failures or sensor failure in either or(I assume both) the upstream and downstream O2 sensors.

The upstream Walker which replaced Denso that I had, but still got the code) are 2 years old with about 13k on them and the downstream (Denso) are about 5 years old, with 25-30 K on them. Previously when I had changed the upstream on 2 occasions, it did nothing to impact the 1646 or 1647 codes. It just seems to me that replacing all the sensors is a waste of money, but worth a try if it makes sense.

I have both the ISCAN and SDD and none of the fuel trims or voltages of the sensors are out of whack or range.

I had pending codes last night, erased them and this morning did the 15 minutes of idle after it was to running temp and I had pending 2096 and 2098. I then took a short drive and I now have pending all 4. I guess I could always have developed some exhaust leak, but this is a garaged car and I don't drive more than about 6500 miles a year and there is no rust as if I were in a very wet or snowy area and I can hear nothing to indicate a leak noise.

I know the testing on the 1646 and 1647, but it appears on the surface to be daunting. I am assuming the the 2096 and 2098 are an extension of the problem that was only 1646 and 1647 before. I have also reset with the battery to let it relearn, but that appears to be of no help.

Has anyone had this experience with all 4 codes or any thoughts, suggestions or ideas as to what to do now. It does not affect the drivability of the car and my inspection is not due for 7 months. It does not have a rough idle and I have no hesitations. Could this be slightly caused by the fact that I do lots of short trips 80% of the time?

I am open to all suggestions except to take it to the dealer as I know the ways on a situation of this nature they would try to exact money from me in their typical unethical ways.

Thanks for any help in advance.

Tom in Dallas /Plano

05 S-Type 3.0 120K

 

I guess you've read the Jaguar OBD docs but to summarise if only for others:

1. P1646/P1647 are about the upstream fuel trims

2. P2096/P2098 are about the downstream fuel trims

#1 are as observed using the wideband O2 sensors, relying on them, their wiring, etc

#2 are the same but the downstreams & they're not wideband

It could be that having P1646/1647 on & off means the #2 DTCs are correct i.e. the cats are not in great condition etc.

hmm... could be, but with what you say I'd be wondering what else.

Ideas:
Water in the PCM? (painful to take lid off it to look)
Wiring chafed/wet/etc? (stare at electrical guide - it tells far more than many realise e.g. splices, grounds, etc)
Marginal power/fuse/relay? (includes battery, of course LOL)

 

Thanks for the response. I would be overly surprised about water in the PCM and would that not affect other systems? The P1646 and P1647 have been with me for many summers. I just went out t and drove the car to the store and the pending on the 1646 and 1647 went away. Still have pending on the other 2.
I have switched relays around before and that went no place. How would you have a marginal fuse? Would it just work or not work? Battery and alternator are new within about 5 months.

The weak cats could be a possibility, but so far no codes related to that or any driving conditions that would point to such. I have had a cat go bad before, so I know what I would expect, but that was one thought I had as well. Looking at the wiring diagram means I have some homework to do and the chafed wiring could be the cause of the resistance issue that NBCAT suggested. Do you off hand know the route of the O2 sensor wiring?

Thanks for your response

Tom

 

For P1646/1647, the first possible cause listed is a failure in the heater circuit:

http://www.jagrepair.com/images/Auto..._OBD_II_R2.pdf

On all 4 O2 sensors, power for the heater circuit comes through relay R2 in the front power distribution box. See figure 01.7:

http://www.jagrepair.com/images/Auto...cal-2005on.pdf

I'd remove that relay and checks the prongs for discoloration, which is evidence of overheating. If good, try swapping with a known-good relay. R6 (wiper high/low) would be a good donor if the wipers work normally at all speeds.

If you do find evidence of overheating, cut a strip of thin metal the same dimensions as the relay prongs. Check each socket individually for a proper grip on the relay prongs.

My hunch is this relay has some internal arcing on the contact points and is reducing the flow of current to the heaters. IIRC, the heater circuit is only active at idle or when the engine is still cold. At higher power settings, with the engine warm, the heaters are not needed for the sensors to be at their required operating temperature. Even though this relay feeds the heater circuit of all 4 sensors, the upstream ones are wide-band and may be more finicky. That might explain why there are no codes for the downstream sensors.

 

Oh, looks like we were both typing at the same time. So much for my theory of dirty contacts inside the relay.

I'd still individually check the grip of each socket for the relay.

 

Thanks Karl. I will check the relay in 2 or 3 minutes, although the last time it appeared fine. I do have downstream codes 2096 and 2098, but these have only appeared in the last week.. All of this happens at idle. It is helpful to know that they become active at idle, although that seems silly when the temperature outside is 100 degrees and the temp on the CCU shows 107 or something like that.

I will report back and see what the relay will look like.

Thanks

Tom

 

It needs the heaters when the O2s are not hot enough - which is around 600C!!

(Actually I suspect that's more like when you've got a good hot engine, but I don't know the actual threshold - which the PCM determines another way, probably monitoring current, as it hasn't got a temp sensor in the exhaust.)

I like Karl's thinking even if it doesn't pan out.

I don't know the 3.0's wiring routes, sorry.

 

I didn't see those codes in the quick reference guide, but they are in the service manual. Do a control-F to find them. The pinpoint tests ask if you have any other codes for 02 sensors, and if so, follow the pinpoint tests for those codes.

http://www.jagrepair.com/images/Auto...M-Workshop.pdf

 

Went out and the relay were in tight enough I had to use small pliers to get them out No discoloration in any way. Swapped R2 with R6 which is the wiper/hi/low switch. Checked the 2 30 amp fuses for the O2 sensors, no indication of anything except a fuse. Attached are the 2 codes 2096 and 2098 and they do refer to circuit failures. It will be curios with the heat coming down some, if they will eventually disappear.

 

Interesting as to how hot they need to be and the 1100 degrees F is about what the Cat Convertors run at.
I have not looked to see if either one becomes red hot, but I would suspect if that happened, they would soon breakdown and die.

Thanks for your thinking and thoughts. Electrical problems and Jags. We thought they disappeared with the curse word: LUCAS. Apparently not.
One suggestion that was very generic was that contaminated fuel would set off the 2096 and the 2098. However I always get QT Prem. which is a top tier classification.

Tom

 

I wouldn't blame Lucas etc as you have about the rarest codes ever. It's something very rare & specific to your car. I can't see it being fuel.

There's more codes/etc detail in the attached. I'm not sure it's the most recent (which will be in the site's large file area I expect).

 

"Contaminated" may not be the best description. Could just be a variation in fuel chemistry.

It wouldn't hurt to try a different brand. Myself, I am very partial to Chevron. Curiously, of late, I have noticed something interesting. One of my cats is marginal, and has been for several years. Intermittently I'll get a P0430 code, pending maybe once or twice a month. But if I fill up at one particular Chevron close to work, I get the code nearly every trip. If I fill up closer to home, the fault goes back to being very sporadic. Same brand of fuel, same grade. But there definitely seems to be something different with that one station.

Based on my over-inflated opinion, I'd suggest trying a different brand for a few tanks and see what happens.

 

Might try that and maybe use the fuel injector system cleaner that Jag recommends.

I do a lot of short drives - 4 miles and under and then at least once a week might do a 40 mile round trip to a client or a short drive to a friend where I might run at 85mph but am there in less than 5 minutes. There is no lack of power. Fuel economy is the same as always. Nothing else is going on to reflect any problem. Jag V8 is quite right. This is a rare code.

TBB

 

So I gets to thinking, looking for a common fault that would affect both upstream O2 sensor heater circuits. I kept coming back to relay R2, but you said you've swapped that with a known-good relay and the fault persisted.

In the wiring diagrams (previously linked), look again at figure 01.7. On relay R2, look at the switched input to socket #1. This is the signal to energize the electromagnet and supply power to all four O2 sensors. The path to energize socket #1 comes from the output of relay R3 (Ignition coils). Now it's easy to deduce that R3 is obviously working, because you have ignition and the engine runs fine. But relay R3 has to energize first before R2 receives its signal to energize.

But what if the internal contacts of R3 are degraded due to arcing? So instead of full battery voltage at R3's output (and thus R2's input), maybe it's only 80% or something like that. This may be adequate for the coils to still fire properly, but this reduced voltage is limiting the power to the electromagnet inside R2. If so, the clamping force is reduced on the contacts (connecting sockets #3 and #5) and you'd get extra resistance. In other words, due to a weak input, you'd also have a weak output to the four O2 sensor heaters.

Being cheap and easy, I'd suggest swapping ignition relay R3 with a known-good relay. Drive for a few days and see if the faults is now gone. If so, R3 was the problem.

Time spent to swap relays: 2 minutes
Money spent: $0.00
Me being right. Again: Priceless


It took about an hour of professional-grade headscratching to come up with this theory. To compensate, you'll need to come to my house and do some chores for the same amount of time.

 

This is the pin out diagram for the PCM. Might help you trace the wiring from the O2 sensors back to the PCM. Which will tell you the condition of the wiring on those circuits.


.
.
.

 

I will try and see what happens. No harm. However if I was getting an arcing on the relay would that not cause a fire or blow out some fuses?

Here is a great example of what happens.

Just to show you how this works is fun. Yesterday I had the 4 pending codes. I had not driven the car from about noon until 6 that evening. The outside temp was down to 90 degrees. I drove through several stop lights where I had to stop, got on the turnpike and for 8.5 miles at about 80 mph. Had to stop at a main stop light and idled for more than 2 minutes and then finally got to my stop about 3 minutes later. All the pendings were gone. I checked it after I got back home- no pendings at all.

The only change is the lower outside temperature.

I will see what happens in driving a more normal speed to the gym and back and see if any pendings come about.

What chores need to be done?

Thanks

Tom

 

Just a heads up that the realize that are in the fuse box upfront come in two versions. One is a 4 pin and one is a 5 pin. Either one will fit in either slot so when you swap and make sure you don’t swap a 4 for five like I did at one point

 

Thanks. I will be on the lookout for that, although I don't remember seeing any of the 5 pin version.

TBB

 

Not necessarily. To blow a fuse, you need an increase in current, that is, a decrease in resistance. Arcing causes pitting, which increases resistance and decreases current flow. That's just the opposite of what overloads a fuse.

Risk of fire? Never seen that happen. Arcing is a common fault, so I'd imagine the designers anticipated the risk and specified fire resistant materials.

Here's a good example of a relay damaged by arcing. This was in the control circuit for the AC compressor clutch on my '02. The AC still worked somewhat, but performance was only fair at best. The arcing limited the current flow to the clutch and reduced the clamping force. This caused the clutch to slip. A new relay restored proper performance. No other changes were made.




Until the wind changes, that's my TheoryDuJour. Like a climate change scientist, it's important to steer the next steps to fit my preordained outcome. From the Cheap and Easy Department, I'd suggest popping off the cover to look for evidence of arcing. Relays are cheap, so it wouldn't hurt to just replace R2 and R3 as a precaution. These are industry standard relays, so any quality brand will work. Any parts store will have them. You don't need Jaguar brand relays. Those are just standard relays in a very expensive box.



My daughter's boyfriend broke her heart, so I need to dispose of his body. The lawn needs to be mowed, too. Either one would be a big help, so take your pick.

 

Thanks. These are Ford relays, so not costly to replace.

Well you are in Oregon and with the increased heat the body disposal appears the easiest. I was brought up by a Doctor.

TBB