Error code P1221 and related questions

Bushbasher · 22-05-2014, 05:35 PM

I just scanned the wagon and got error P1221 and now I'm a little worried but also a little confused. Forscan says it may be a faulty or damaged PCM or a short to power or ground in the VSS or a VSS open circuit. I checked the PCM to see if there was any moisture getting to it but it all looks A ok so I've ruled out external damage to the PCM. So I have a few questions....

1) Can there be a short or open circuit in the VSS if the speedo is still working correctly?
2) If so, what's the easiest way to get at the VSS module? From under the car or through the shifter hole from inside the car?
3) Is there any other obvious point in the wiring loom that would cause a short in the VSS circuit?
4) Is the VSS in any way linked to the engine operation directly that could affect fuel mileage as that's what prompted me to go looking for faults in the first place?

Any help on any of the questions would be greatly appreciated.

Cheers
Bushbasher

**auIILTD** · 23-05-2014, 10:58 AM

Hi Bushy

From the DTC section on here, here is a more detailed description - Click on DTC's on the menu bar above if it appears for you? It maybe a DM only feature?

P1221
Traction control system malfunction where applicable DTC P1221 is reported if the there is a communication fault between the Traction Control Module (ASR) module and PCM

Improper connection, short to Vehicle Power (VPWR) or ground in Vehicle Speed Sensor (VSS) connection between ASR module and PCM. VSS signal open circuit

Faulty ASR module, refer to Group 2, Brakes. faulty PCM

Cheers
Stu

Bushbasher · 23-05-2014, 12:05 PM

Thanks Stu, but I got all that. The Forscan says exactly the same thing but it won't tell me the answers to the questions I posted mate.

Bushbasher · 23-05-2014, 02:18 PM

Ok, I've worked it out. The other day the weld on the back of the resonator let go so I had it mig'd back up till I can organise a new centre muffler and in doing so we disconnected the battery. Well it seems when I re-connected the battery I didn't get a good enough connection even though it was good enough to start the car. Last night after musing on the problem for a while and deciding it made no sense that there could be a problem with the VSS if the speedo worked and as the car doesn't have traction control, it could only be a bad earth. So just in case it was a PCM issue I disconnected the battery and left it overnight then re-connected it today with a nice tight connection and tested it again and everything s' hunky dory and no errors popped up.
But that does mean the slowly degrading fuel economy, which started this whole hunt in the first place, must be down to the dodgy exhaust.

james22 · 23-05-2014, 03:40 PM

I've had this error code pop up ever since I bought my xr8, seven years ago. The speedo always worked and there were no earthing problems. So I always assumed it was just because my car was an OPT20, and therefore had the adjustable speedometer.

I've disconnected the VSS, tested it, cleaned connections, checked earth and always had the code. So it never really bothered me.