Hi all — I have a '92 Volvo 960 with an intermittent transmission issue. I get the dreaded flashing yellow arrow + flashing W/S/E, and then I'm in winter mode (or possibly limp home mode, hard to say), with inconsistent shifting at highway speeds and no first gear... and then it goes away.

I replaced the PNP (aka Neutral Safety Switch/Gear Position Sensor) 4.5 years ago, and while it's definitely possible that the switch failed again, I'm inclined towards replacing the TPS first, for the following reasons. But maybe I'm wrong! And I'd be very grateful if someone with more experience could offer advice on the correct diagnostic/repair procedure, given my "symptoms." Is there a clue here that points you in a different direction? I'm trying to get the car road-ready for a long trip next week; here's why I've ordered a TPS:

1) OBD-1 (Port A-1) shows code 2-2-3 ("Throttle position sensor signal too low"). No CEL, and that's the only code I get.

2) When the flashing arrow is present, I am unable to clear it with the classic PNP switch "clear the dirty contacts" method of diagnosis/temporary repair. (Where you slide the gear selector through all the gear positions.) I also still have my rear backup lights, and again, no codes indicating PNP fault.

3) When the flashing arrow is present, the transmission doesn't know when to shift (at highway speeds), and the tach twitches between 2,000 and 2,500 rpm in an unhappy state. The last time the arrow "arrived," it happened right as the trans shifted into 4th gear.

4) Before I had this yellow arrow, I experienced another possible TPS symptom: a sudden-onset, fairly noticeable decline in throttle response, during a long steady highway drive. I really felt like I had to give the accelerator more input to maintain speed, so I ended up just driving slower. No CEL, no arrow, and this has not happened on any of my subsequent long drives... nor have I stalled, been unable to start the car, or had any other issue.

Also worth noting:

*) My W/S/E transmission mode switch was a bit crusty, and I hadn't touched it in years (nor had I spilled anything on it, to my knowledge)... until recently, when I switched to "W." Shortly afterward, this problem emerged. Spraying it with WD-40 made the problem go away for a short while; removing the switch and spraying it with contact cleaner made it go away for even longer... but my mechanic has suggested that those were both just coincidence, and it's not worth replacing this switch, it's rarely the problem...

*) The previous owner also experienced a flashing yellow arrow, startup in 2nd gear, and according to his service records, he had the TCM replaced (!!), and transmission flushed. Yowza. My transmission fluid is still red (and if anything, it's a bit high on the dipstick), but I've had no other transmission issues in the 4.5 years since this was done.

*) A few months back, I had an "fuel trim limit high" code — as in, the car was running rich. After the car sat for a month, the code reset with a dead battery, and has not returned even with 2,000+miles of highway driving.

THANK YOU!