P1312: How to check for bad wiring?

[SantaCruz]

Dear Saab friends,

Occationally I get the P1312 error code on my 2004 Saab 9-3 2.0T Arc -- often when going highway speeds up the hills. I've replaced the four spark plugs with new ones NGK PFR 6T-10G as recommended (gap checked) and tested with four (black top) known good coils and a known good CDM module from another Saab. Error persists, and running out of good ideas I wish to check the wiring for eventual bad connections.

Would there be a good way to check the wiring and where would I connect my ohm-meter? (Pins?)

Thank you very much for any hints and ideas.

[Digger]

Dear Saab friends,

Occationally I get the P1312 error code on my 2004 Saab 9-3 2.0T Arc -- often when going highway speeds up the hills. I've replaced the four spark plugs with new ones NGK PFR 6T-10G as recommended (gap checked) and tested with four (black top) known good coils and a known good CDM module from another Saab. Error persists, and running out of good ideas I wish to check the wiring for eventual bad connections.

Would there be a good way to check the wiring and where would I connect my ohm-meter? (Pins?)

Thank you very much for any hints and ideas.

Never been to Santa Cruz, but if it is as hilly as San Fran your occasional up the hills at highway speeds P1312 might only be fuel, or fuel and mas air sensor related, or your plug gaps might not be the same exact mm on all 4, or there might be a weak connection between the ION module and one or more coils,

Start with your fuel, premium from one station might run better in your car than the premium from another. Run a couple cans of Seafoam through the system with the next couple of tank fills to clean injectors and any carbon from the pistons.

There is no good way to find an occasional under load error code with an ohm meter, but you will find the how and where to check the possible wires in the WIS and you can find a link to download this manual in the first sticky of the Tech Talk section.

[SantaCruz]

Thank you, Digger,

Now with WIS, my initial question has been solved, but solving the issue is still 'work in progress'. In short:
- Cylinders are numbered 1 thru 4 from passenger side toward driver side.
- Error P1312 concerns cylinders 1 and 2 (, while the equivalent P1334 would have concerned cylinders 3 and 4)
- Error codes P1312/P1334 possibly concern ionization signal out from coil pin number 4 (bottom pin of connector #320a-d) to CDM (connector #740 pins 16,7,8,15 for cyls 1-4, respectively). Imprint markings on the CDM also show what's what, and verified by ohm-meter.

Will test the effect of higher octane gas at next fills. Would possibly expect choosing a certain octane couldn't be the sole problem, since the error code is a recent issue, and would possibly also then expect to see both P1312 and P1334 if fuel issue. I only see P1312.

I moved spark plugs and coils to different positions in the engine ( 1 and 2 moved to 3 and 4) to test if that may trigger P1334 instead of P1312. It doesn't and P1312 persists -- possibly indicating no single spark plug or coil is to blame.