...stumped because as of today I checked the wiring to all the 02 sensor for chaffing etc. No problems found. Also disconnected and reconnected each to check for a good connection.

I then hooked up my scanner then fired up the jag to obtain live data. I paid particular attention to the voltages and current reading for the 02 sensors on both banks...virtually no difference. At most the voltage readings between the two would be .010, but usally only .005, whenever they would differ.

After the car had reached operating temperature, I cleared the code and drove down the road for about 3 miles, watching the live data stream. The CEL never came back on...until...I decided to park and remove the key for a couple of minutes. Upon restart, the CEL was lit and the scanner indicated P1647 was back. Again, monitoring the live data the readings for the left and right bank sensors were almost identical.

Suggestions on what to check next?

 

HO2S heater failure
HO2S sensing circuit short circuit to
ground or high voltage
HO2S sensing circuit open circuit
ECM failure


I wonder if starting the car introduced a high voltage pulse to the sense circuit? Just a wild thought- I would check the engine ground strap on both ends. Then you might try swapping the left and right upstream sensors for a few miles and see if you get a bank A fault. I would not leave them swapped too long, as it will certainly screw up the adaptions. As I beleive it was Thermo pointed out before, you might just have a bad ECM, but thatis rare.

 

Thanx for your thoughts Ross. Because I can monitor the voltages while operating, I'm ruling out the possibility of an open circuit, short circuit or high voltage.

I guess that leaves the possibility of the bad heater or ECM. Although, I would think if it was the ECM I'd still see a problem while the system is running??

I guess my next move will be to check the ground straps and swap the connections as suggested and see what happens.

Thanx Ross.

 

I would guess bad heater. You won't see that on a sensor readout. I would agree with sparkenzap, briefly change the connectors over just above the transmission and see if it changes to a P1646. Alternatively, use an ohmmeter and measure the heater circuit (black pair) which should be around 6 ohms or so. The ECM monitors the heaters at start-up and if it finds a fault it ignores the sensors, lights up the CEL, keeps the fuel system in open-loop mode and uses a pre-defined engine fuel map. It doesn't stop the sensors from working so monitoring them doesn't give a great indication at all, eventually they get more or less to temperature but the wideband O2 sensors rely a lot more on the heaters to keep their temperature in the working range which is why they get ignored by the ECM if the heaters fail. BTW they are constant-voltage variable current sensors specifically designed to be insensitive to voltage spikes.

Jim

 

Thanx guys.

Well, swapped the leads, cleared the code and fired her up. Let it run for a few minutes then shut 'er down. Turned the key back on, checked for codes and there it was...P1646...moved to the other side.

Next stop, the parts house for a replacement...then try to figure out how to get to that damn thing. it would have to be on the side where I can't even see the darn thing from above...and struggle to reach from the bottom.

Thanx again for your assistance.

 

Sounds like you got some good advice crosbo, great job diagnosing Ross and Jim!

 

Just replaced o2 sensor upstream passenger side.
Cleared code and took for a ride.
Car is very sluggish.
When I checked codes the damn 1647 is back!
I switched connections 1646 comes up.
What else could cause the code with a new sensor installed.
And would a bad sensor be the cause of my car being so sluggish?
Idles fine, dosent appear to be missing, but has no pick up.
Just replaced fuel pump and filter appears to be plenty of pressure.

 

What sensor did you install?

Did you check to make sure you had the direct fit replacement ?


You could have a relay problem that turns the heaters on. I forget the fuse situation for the heaters - even though I just went through all of this

 

replaced with Bosch 15627.
Fuses good relay good.

 

cbg....
I would say you need to figure out if you have the right sensor.... Year models are sometimes murky for these cars, so you need to know if you have a wideband sensor or not. Do both pre and post cat sensors have 4 wires? Apparently the wideband sensors have the same connector as the earlier ones, and are absolutely NOT interchangable. I THINK the part # you have is a wideband sensor, and that goes on the later models. You should have heated sensors for all 4 positions.

 

Every auto parts site I checked has bosch #15627 as the correct oe fit.
Did I change the wrong sensor? I seem to be getting conflicting info regarding the location of the sensor for the p1647 code.
The one I replaced is on the passenger side on top, easily reached with 22mm box wrench.
If this was cause of the car being so sluggish would changing the sensor give me immediate
results? Or will it take time for the computer to recognize the new part?

 

Not sure #15627 is correct - this thread might help. I have seen a few posts about fitting the #15627 and it hasn't worked. I have seen a few sites list it as suitable for pre and post-cat and that is definitely not right.

Perhaps this thread might help?

https://www.jaguarforums.com/forum/s...t=23263&page=2

 

On my 2002 XJR -- This is a USA spec car.

Only my pre-cat sensors are 4 wire heated -- the post cat ones are two wire non heated.

 

Well after changing the fuel pump, fuel filter, oxygen sensor, looking for a short for 3 days, which turned out to be the fuel inertia switch. I changed 4 of the spark plugs and car ran like new. So I figured if I changed the other 4 plugs it would run better than new, wrong!
After changing the 2nd set of plugs went back to being very sluggish. Now 2 of the first set of plugs had some oil on them as did 1 of the second set. I have read that a clogged PCV valve could cause. Where is the Pcv valve on a 99 VDP, hoping for an easy inexpensive fix,
as I have been bragging about the fact my car is great and only have had to do minor fixes
contrary to the belief that Jags are very unreliable and very high maintenance.

 

cb, I'm going to go out on a limb here, and reply that you don't have a pcv valve. What you should have is: 1) Forward end of passenger side valve cover is a ribbed breather tube 3/4" that goes into your inlet air duct, 2) on the forward inboard upper end of drivers side valve cover you should notice a smaller 3/8"? tube called the part load breather tube. This has been know to become clogged. Disconnect this a run a 3/32 drill bit down through hole / fitting in valve cover to ensue it is free of sludge, etc. Be careful, and don't drop bit into valve cover. I'm not sure if this is the root of your problem, but if it is clogged it WILL give you problems. Check out Gus's site for " lean codes left & right banks", I think he discussed this there.
Good luck.
Ralph

 

The LH sensor can be reached by removing the coolant tank and exhaust manifold heat shield. A 22mm crowsfoot will fit the sensor. Not a lot of room but doable.

 

I am certainly not an expert on Jag part numbers BUT I BELIEVE you have the sensor configuration of a MY 98 engine. I say that because you have two wire sensors post cat which are definitely for the AJ26 engine variant. The wideband sensors only go on the later engine which has an AJ27 designation. What I am not certain of is that the Bosch number you describd is for a linear sensor, although I THINK it is. I know it is used on the later engine, but I do not know if it is used as the pre (wideband , linear) or post cat (heated, discrete) sensor. Year model designations are not accurate in parts books, only VIN or engine numbers.
BTW- "EVERY parts site" uses the same data from the Bosch listing!

 

Rae by looking at Gus's site I have found that the hose you are speaking of is attached to a breather stub. Have you removed yours?
I can't figure out how to detach the darn thing!
It has a little plastic clip shaped like a horse shoe witch I removed but the hose just wont come off. Also the stub appears to be connected to the valve cover with some sort of adhesive and doesnt appear to be air tight?

 

cb, you're at the right spot. Mine has a "Norma" fitting, circular, sqeeze opposite sides and it will come apart with the hose in tow. Not sure about "horseshoe" shaped fitting. Either way, the hose should come out, leaving the fitting in the valve cover. You can then look into fitting and see the hole you want to make sure is clear of crud. The fitting is RTV'd or some other mucky puck into place. I would not remove it, unless I had to, then be sure to reinstall with some type of heat rated RTV. Be carefull, they will become brittle over time from engine heat. It's been awhile since I looked at mine, but it may flow into inlet air side before throttle body, and if it's loose could affect your air/fuel mix resulting in lean codes showing up. You might want to post a new thread regarding "part load breather tube" and see what kind of input you receive. Good luck.
Ralph

 

There's also some pictures and some description about how to get that part load breather fitting off in our FAQ thread in the XK8/R section. Find under the engine section a link to cleaning the MAFS, throttle body and part load breather. Its pdf. g'luck