Anyway, the dealer called again yesterday. They weren't sure what was up but they thought that the next best thing to do was to replace the MAF. Replacing the TPS would cost $3400 just for the throttle body assembly not including labor. They also told me that they checked the wiring harness and it was ok. They said it showed .3 ohms which seems a little high to me (resistance calculator said 6ft of 28 awg was ~.1 ohm but whatever). I told them I would take delivery of the vehicle as-is.

Replaced the MAF sensor with a rebuilt one from advanced auto. I did this in the parking lot of the dealership. The replacement sensor had the exact same form factor as OEM but it had different looking filaments and also only 2 filaments instead of 3 like the OEM MAF sensor. It also had 2 fewer pins on the connector than the OEM sensor. I noticed that the cable leading to the OEM sensor had 2 fewers conductors than the OEM sensor itself so it seems that missing that third filament doesn't matter anyway.

That solved the problem. I started the car about 10 times to test it and it had no problems.

Thanks for all the help everyone!

Just remember to not go rushing to replace your batteries as soon as you have any sort of random unrelated problem.

 

Yeah all manufacturers have proprietary PIDs and some are secret and some are published but that's besides the point. Reading diagnostic trouble codes is done under "mode 3" operation as they call it and that mode doesn't have anything to do with PIDs. Mode 3 just dumps data.

 

If the MAFS fixed the problem then good for you. Only time will tell!

 

RE: "hidden codes" and RP

I'm in the process of diagnosing a P2601 (supercharger coolant pump circuit range/performance). One thing I notice is that when this code is thrown, the car immediately goes into RP. Makes perfect sense. When the code is cleared, you have to shut off the car for a minute or two (I haven't timed it exactly), before RP is cleared. This has the effect of seeming like a "hidden code", when it's really just an alternate engine management state (kind of like open-loop vs. closed loop).

tl;dr - there may seem to be hidden codes if your OBD tool doesn't read a) PIDs that it doesn't know the definition of, b) pending codes, c) alternate engine management states which aren't emissions related. Open-loop vs. closed-loop is emissions related, so all scanners should read these. RP or limp-home is not an OBD thing, so (probably) only Jag diagnostic gear will be able to reset those on demand. (Caveat - some scan tools allow access to a command console where you can send commands directly to the ECM - these will allow a far greater range of troubleshooting activities, but you MUST know the command format, and you take the risk of bricking your ECM)

I've had a couple P1121 codes and have ruled out battery failure, so I'm moving on to MAF cleaner. The P1121 are extremely intermittent, with no real correlating factors (yet), so it'll be weeks before I can tell if it's cleared up or I need to buy a new MAF. My car has a little over 100k miles on it. I figure the OEM parts have carried it this far, so I'll go with OEM parts for replacements (there's no chance I'll put another 100k on this car before I replace it with either an F-type or an XJR

One last thing - my scan tool will read *every* PID. They were clever, and only allow reading mfr-specific PIDs, for which they have no metadata, in dump/log mode

Ken

 

It has to restrict performance if that coolant pump doesn't work right else the charge air is dangerously hot.

It could be wiring etc but it always seems to be the pump.

You're getting rare (P2601) and unique (P1121) codes for an STR. Er... congrats?

If not the battery, might even be a wiring problem.

P1121 is probably about either the throttle pedal (accelerator pedal) or the throttle sensor - it's not even in the usual codes info or the Denso info for the S-Type after 2002.5MY.

I hope you realise your STR is extremely unlike the 4.0 for the rest of this thread. You have lots of things the 4.0 hasn't and vice versa. Even the PCMs are not just different but made by different companies (based in different countries). And of course the 4.0 hasn't got the SC coolant pump that's causing P2601 (as it hasn't got the SC).

 

I hadn't checked back in on this thread in a while, and I just noticed a response I don't believe I was hoping to equate our ECMs or the nature of the codes - just saying that I had experienced behaviors that could be construed as "hidden codes" where where, in fact, not.

Thanks for the info about the TPS - I've continued to get 2601 and 1101 (or whatever the MAF circuit low code is - can't remember off the top of my head). The rule-out process has been slow and methodical, including replacing the MAF with the wrong one for the car (got a non-SC part, whoops), which led to massively rich behavior for a few miles until I ripped that thing out. Just ordered the proper MAF, and I have a new SC pump ready to go in, so we'll see if I just threw away $550

Thanks