Hello AG,

I'm working on a similar issue with my 1999 945T with a long term bug in my car going back for some years reported by the previous owner.

You can check your CPS with an ohmmeter and see 179 ohms between pins 1 & 2
Then using your VOM's highest resistance scale check for a high resistance short
between ground pin 3 and the two others .

Do as Dave says check for OBD codes, and find out how to use the special modes.
I think they wont report RF corruption directly.

Before your car outright refused to start, did it misbehave by stalling at stop signs or traffic lights? Mine suddenly did this followed shortly by a refusal to start.
I found that I would get a code A6 2-1-4 (faulty or sporadic RPM signal)

Then I could disconnect the battery to clear ECU memory, and the car would start and run normally. See if your car responds this way.

I think that the geriatric ECU's are more sensitive to RF corruption EMI/RFI via
the CPS because of weak aging filter caps. This is certainly part of the problem.

My CPS is a cheap Chinese after market unit, and I suspect the difference between it and the OEM CPS is partly on the quality of the connector which is
probably carefully plated in the OEM and plain steel in the cheap one.
Also the harness shield is of major importance. I found the shielded wire to
be a disappointment since it consists of only a piece of aluminized tape surrounding the signal wires. If the CPS harness sheath has started to crumble
then the shielding is toast and you can expect problems. Corrosion at the
connectors is also a huge issue over time and worse if it's a cheap connector to start with. Spook is right to service the connectors. He likes DeOxit
and I like Penetrox-A, I suggest that you service your CPS connectors especially the female EFI pins in the harness connector. Use a toothbrush and
90% isopropyl alcohol and blow out with air. Then carefully inspect each female pin for damage. Volvo says to test each female pin with a gauge made of a male
EFI pin to insert and see if the female pin grabs and is not loose.
I'll order one myself when I place my next order to www.davebarton.com this week.

In addition to disappointing automotive quality of the harness shield, the connectors are also NOT shielded, again automotive quality connectors.

After servicing the CPS and AMM connectors and lubing with Penetrox-A I placed
snap ferrites (RF chokes) on the CPS harness , one at the bell housing and one near the harness connector. I did this because 1. Volvo does not ground the RF shield at the bell housing and 2. the connectors are un-shielded.

My issue quieted down dramatically after adding the ferrites but recently I checked the OBD had thrown another disturbing A6 2-1-4 , this time with no
engine malfunctions. So I ordered 1 meter of 28MM ID tinned braided copper EMI/RFI shield that I hope will pull over the CPS connectors. This is scheduled for delivery today, It will hopefully pull over the connectors to improve the
EMI shielding. I plan to ground it at the firewall and leave it ungrounded at the bell housing for now. This is a work in progress.

Provide an email address in case Brickboard decides to gag again.

Good luck, Bill