OK this is fairly embarrassing as my first real post to this forum, but I have searched around for a while and not discovered any source of clarity.

• Car is a 2000 XKR.
• Issue is a compound one of multiple P-codes, made worse that I am now suspecting my code-reader is unable to see real-time data.

Background - skip if you don't need it.. Upon buying the car it was very down on power and throwing CEL for Bank-B upstream O2. I replaced both upstream, and downstream O2s (4 in total), as well as new plugs correctly gapped and finally cleaned MAF. EG: basic tune up and baselining inclusive of validating both FP's work and both were able to support starting/idling/driving the car with the other disconnected (sufficient flow). Drivability got massively better over a couple days and CEL went out. Happy joy, plenty of usable power.

Recent Change: A couple days ago CEL came back - and now I'm seeing codes (remember I am dubious on my reader) that indicates both banks too lean, and both banks too rich - and the O2 control plane etc... Smorgasbord... Car is drivable albeit w/Restricted performance warning and I cannot access as much power as was there a day or so ago. Mode code reader also seems unable to trigger a DTC erase. Erase request gets sent but never happens. Meanwhile it shows all greens on Drive Cycle Readiness and P1111 is set. I thought those things would be mutually exclusive of each other.

The desire: as O2's are only 4 wire I thought let's follow JTIS and make sure we've got power, Gnd and Signal all getting where it's supposed to go and not shorting to Gnd. That way I'm down to probably having installed a new-sensor that already went-bad. Unlikely - but has happened to me before. But honestly - I get lost in the procedure in JTIS because it's not abundantly clear (or I'm being dopey) when I'm measuring a connector on the chassis harness vs. the ECU or the sensor itself. Therefore - is the below process close enough to exonerate the wire paths?

The questions:

1. The white/green-stripe wire that supplies voltage to each O2's heater -when key on or engine running that should be sending battery/alt voltage to pin-position 2 on: EM21 through EM24 plugs yes? Anything less than batter/alt voltage = solve that first right?
2. O2 Heater-Gnd is what the ECU provides/observes for the heater element and therefore I need to ensure continuity, and no other path to Gnd between
   • LHD Passenger Side Upstream O2 harness connector EM21 pin 1 and ECU plug EM85 at pin 01
   • LHD Driver Side Upstream O2 harness connector EM23 pin 1 and ECU plug EM85 at pin 01
3. O2 Signal-Gnd is ECU provided and I need to ensure continuity, and no other path to Gnd between
   • LHD Passenger Side Upstream O2 harness connector EM21 pin 4 and ECU plug EM82 at pin 10
   • LHD Driver Side Upstream O2 harness connector EM23 pin 4 and ECU plug EM82 at pin 11
4. O2 Signal is provided to the ECU from the sensor
   • LHD Passenger Side Upstream O2 harness connector EM21 pin 3 and ECU plug EM82 at pin 04
   • LHD Driver Side Upstream O2 harness connector EM23 pin 3 and ECU plug EM82 at pin 05

And if all that checks out with no leakage of any path to Gnd to unexpected voltage = wire path is good, now is either an issue in the O2 sensor itself, or in the ECU itself. And if so - assuming I chuck my OBDII reader in the trash do I need to step up to JLR Mongoose because I'll need it eventually - or is there a good alternative?

 

For the heater power and ground, you need to test these at the connector that the sensor plugs into (unplug the sensor first). The best way to test is with a 12v bulb. I don't know how much room you have to get at the connector, but you could cut the plug off one of your old sensors and use that as a test plug.

For the signal wire/ground, you need to check that at the ECU end - unplug both ends. With a multimeter check for continuity between each wire in turn and the chassis/ground - both should be open circuit. Check for continuity between the two wires - again it should be open circuit. Now short the two wires together at the sensor end - your multimeter should show continuity/low ohms, if not you have a break in one of the wires.

For your OBD reader - my cheap bluetooth dongle and Torque app shows real time data - can you see no data at all, or can you see values that aren't changing?

 

An obvious point but how old is your battery and what voltage is it supplying before you start the engine?

When either of my Jags suddenly start throwing misfire/fuelling codes, I simply charge or replace the battery and clear the codes and everything is fine for a few more years.

Richard

 

Thank you @Dibbit - that is the clarity I was looking for and we're on the same wavelength. To answer your question my OBDII reader is brand: Zurich and model ZR11 and no when selecting the view live data function it never is able to make the live-data connection. I'm going to try with my laptop and Ross-Tech software that is Audi specific but has OBDII general functions as well to see if I get a different result. I appreciate the input.

@RichardS - I have two batteries actually. Both AGM and one brand new. That was the first thing I changed out have read post after post about that being a likely cause. But since I didn't mention it in my history I appreciate you bringing it up. And just to be triple-darn-certain - I'll chuck the charger on it now and make sure it's tippy-top charged.

 

oh and @RichardS - the key on, not running base battery voltage is measured on my Fluke DMM on the white/green-stripe wire of the O2 heater circuit as 12.54v and then started/running is 14.2'ish. I have not checked voltage-drop during cranking - but as stated above the battery is new within 30d and a correct high-amp AGM unit.

 

12.54V is good. I find that the problems don't start until it drops below about 12.2V.

Richard

 

Wow what a difference using the Ross-Tech software was over the Zurich Code scanner! Not only was I able to actually clear the smorgasbord of codes that were present - I was able to see and log live data too! Sadly I can only graph/log 4 channels in parallel. Picture A is the array of codes I had been unable to clear with the Zurich. Picture B is the result after DTC clear using the Ross-Tech VCDS in general OBDII mode. Now the pending P1000 code is still present until I do drive cycles - but so-far I am hopeful that the O2 codes are gone.

P1642 will become my focus. I do also have ABS / Trac faults - so I will be pulling the ABS computer to do the re-solder trick today. Is there anything else in there I should deal with related to CAN-bus termination while I am "in there"? Or is this a pull it and send to Module-Masters situation?

Smorgasbord - Picture A codes that the Zurich ZR11 handheld scanner would not clear

Result after using Ross-Tech VCDS software in standard OBDII mode.

Able to read live data early in the first start of engine post code-clear.

 

Well the change in the OBDII reading is pointing me away from the O2-sensors - so I'm going to declare that until new codes appear - I will trust the readiness read out that says the O2 signals (all 4 are) are within spec. And now I will turn my attention to the new codes being persistent. Thank you for the commentary thus far.