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I'd say you can trust the P1646 is about the correct location of the sensor - it may not be the actual sensor (could be wiring, fuse, whatever) but nearly always is the sensor.
As they're current-sensed... how did you test it? The PCM is quite fussy in its testing if that helps.
Workshop manual, second edition (for 99-2002 cars) located in the second post in this thread: "WORKSHOP MANUALS - PDF Format" https://www.jaguarforums.com/forum/x...ts-data-29800/
specifically https://www.mediafire.com/file/ldfaeda4io2o16j
You'll find diagnostic procedures for the wiring faults in there under the relevant fault codes. Make sure you are looking at the procedure for the NA car. Be wary of the O2 sensor DTCs, depending on your cars year, because there are definitely mismatches between documented DTCs and the actual DTCs my car has thrown in the past. theres a series of tests to pinpoint where in the wiring you have problems when it comes to P1646.
good luck! In my case I just needed a new sensor, but it sounds like you may have a wiring harness fault. Maybe as simple as unplugging the ECU end of the harness, spraying with contact cleaner and re-connecting?
You will probably also need the electrical guide to identify the connectors, pins, wires etc. Also available in that thread.
Hey just an update on my findings. I made a forum at a point explaining the issue and one person mentioned capacitors that could be related to the issue. Replaced all with brand new ones from Digi, didn't do anything other than fix the rough/irratic idle at times.
After
Before
I'm left with the fact that it may just be the sensors from RockAuto. Which all of them are denso 192400-3101. The one I pulled from the car that was bad had the same part number on it with of course a different date. Of course I wouldn't know if maybe it was changed to one that still didn't work via a old owner but who knows (192400-3101)....
In some forums I read some individuals stating the car depending on engine needs a specific sensor with a level of resistance which I'm not too sure on how true that is. But at this point any direction is welcome. I tested the wire harness and inspected it, no tears or burns or in the sock/grommet. ECM for sure now works at 100% no more malfunctions.
The only other test I can think of is swapping the connections for the two upstream sensors to see if the code changes via priming system check on the dash and allowing the code to represent itself.
For p1646 the current code it only appears (if cleared) after driving, no matter how long until you turn off and on again.
If anyone knows the correct part number if I'm wrong please provide it. I just want this code done and gone with.
At the moment IDS still isn't an option until my windows xp pro comes from eBay so I can run jlr 131v.
The only other test I can think of is swapping the connections for the two upstream sensors to see if the code changes via priming system check on the dash and allowing the code to represent itself.
Given you have tried everything else, that has to be worth trying to see if you can eliminate the wiring. It's hard to believe you have got multiple bad replacement sensors, but stranger things have happened. BTW good job on re capping the ECU
Thanks! I had practice soldering for a bit before I felt comfortable doing the ECM. There's two cap
points that have the closet point to other elements of the board which made it a bit dangerous
According to the workshop manual, I believe it's for an 02 sensor/circuit fault. But considering unplugging the other sensor yielded two other codes for voltage within it could be. I'll try to research further but all the forums go back to one thing the 02 sensor. I saw within the manual for s/c that it's for fuel pump 2 but I don't think believe this goes for a regular 4.0 xk8. Correct me if I'm wrong
My car is a 4.0 XKR so definitely does have a second fuel pump relay. Having the same code number for different faults on the same base engine is beyond crazy. I can only assume it would be some kind of hangover from the early supercharged cars.
That post you quoted above, goes on to say:-
4.0L cars, SC/Non SC, P1646 = Fuel Pump 2 Fault [of course, Non SC don't have a fuel pump 2]
4.2L and V6 Cars, P1646 = Heated O2 Sensor Fault
Maybe someone else can confirm this before you start soldering a new harness in place.
My car is a 4.0 XKR so definitely does have a second fuel pump relay. Having the same code number for different faults on the same base engine is beyond crazy. I can only assume it would be some kind of hangover from the early supercharged cars.
That post you quoted above, goes on to say:-
Maybe someone else can confirm this before you start soldering a new harness in place.
I agree, learning that fact was beyond crazy when viewing the workshop manual. In it it states that only a second fuel pump relay exist, and fuse if the car is s/c. But if someone else could also confirm it would definitely clear the air more if specifically the 2000-2001 my is setup in this manner.
And thanks for sharing this info! Definitely was new to me.
Yes it is odd - the only reason I brought it up is because the DTC list for my car shows it as being for the fuel pump. Download the correct list for your model year car from Jagrepair (listed as Engine Management):-
You can check your model year from the VIN number.
Maybe this is just a red herring as we don't have the exact same car, but definitely worth double checking.
Thanks for all the help guys, after a very long thread I finally found the problem thanks to the workshop manual. After confirming p1646 did mean 02 sensor issues(open circuit) was for my car I went ahead and start checking the harness. The previous owner clapped the connections and it read high resistance. Here are pictures, I didn't notice it the first times as it was wrapped in electrical tape
As for my remedy I'm open to anyone educated in solving the high resistance. I'm about to do some research to correctly fix this bad job causing the open circuit
Also further more whatever they did to the passenger side (1646) they did to the other side (1647) but the remedy they did fixed it but not 1646. My guess is the broke or tore and they added that white jump wire. Is my best guess
My guess would be that the taped area holds the key to a solution. Some where someone used a heavy wire where a thin one should be.
Good catch, you have amazing patience.
As for my remedy I'm open to anyone educated in solving the high resistance. I'm about to do some research to correctly fix this bad job causing the open circuit
0.7Ω isn't necessarily a high resistance. What two points were you measuring between?
You could switch the meter to volts and measure across the same two points with the ignition on to see if there's any voltage drop.
Does your meter properly read zero ohms when you short the probes together? I say that since mine shows around the same resistance in that state.
0.7Ω isn't necessarily a high resistance. What two points were you measuring between?
You could switch the meter to volts and measure across the same two points with the ignition on to see if there's any voltage drop.
Does your meter properly read zero ohms when you short the probes together? I say that since mine shows around the same resistance in that state.
My apologies, at first I thought it read in M when I recorded it when it was just ohm so disregard that update. ButI moved to another source possibly being the issue which was the grounding point. Yes( R) to R has good resistance. And Yellow was good as well so the harness checked out getting to the ECM.
So excluding the wire harness itself and the ECM I found that the ground was rusty and corroded. For EM1 within the (Main power disruption). After testing ground like the workshop manual sated the voltage was low and somewhat unreadable. I have one connection to the battery and tested the other prob to the wall of metal connecting to the ground as per procedure. I did this to some other ground points which tested fine.
Tomorrow I'm going to disconnect the battery and clean the ground points and inspect the cable just to be sure it's not damaged and see what happens from there.
05-01-2024, 04:51 PM
