My 1992 Saturn SL2's check engine light came on the other day. Read the codes by shorting pins A and B. Code is 26. Any ideas how to troubleshoot this? I checked the impedance on both the EGR and Purge valve solenoids. Both measure 40 ohms. Any guidance would be greatly appreciated.

 

Oh Joy, a quad driver fault. Oh the memories

Here's one of my responses from like 18 years ago, pasted here for convenience.

Code 26 is a "quad output driver fault".

Several different devices/sensors share a portion of the PCM's functionality; if any one of these devices misbehaves, it can trigger a code 26. Note that in general, it is almost never the PCM itself that has a problem -- it is one of the devices or sensors tied into this circuit that is throwing the code.

Things normally on this circuit for the S cars are
1) SES light itself
2) Coolant Hot (idiot) dash light
3) aux coolant fan relay
4) A/C clutch relay
5) speedometer cutout circuit
6) Upshift dash light / Shift to D2 light (Man/Auto trans, resp)
7) EGR Solenoid
8) CCP solenoid (charcoal canister purge)

Check in the order listed. I know you have already tried to test the EGR solenoid and the purge solenoid. They appear to still be continuous but That does not guarantee proper operation.

Now that I think about it, the EGR up to 94 was vacuum modulated so I need to go check a book to see which solenoid they are talking about.

Note that I have gotten a code 26 when reassembling my dashboard after trying to reattach the ribbon cable that connects the instrument cluster to the wiring in the car. Turns out I hadn't cleaned the contacts well enough and something wasn't making proper contact.

Do you have any operational symptoms with the car in terms of it misbehaving?