Just recently had a bit of a puzzling issue, car was running and driving like normal, but the check engine light would come on anytime I went above 40, and shut off when going below 40, checked the codes and got 3 code 26's. I cleared the codes and drove the car around again, and no check engine light! Any thoughts on what this could be?

 

When was the last time the car had a tune up? Spark plugs, wires, fuel filter and de-sluding the throttle body will go along way in curing driveability issues with later model Oldsmobiles.

 

Have you googled that code? You get lots of results if you do. This is from a Saturn forum. Not Olds, but GM nonetheless, so I would think that code numbers would be similar.


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 the above in the order listed.


I also came across this, which might be relevant since it involves the transmission, and your issue is apparently speed related.

The Transmission Electronic Control Unit (TECU) monitors engine speed and Input Shaft Speed Sensor values to calculate clutch slip. Fault Code 26 indicates that a clutch slip event has occurred.

 

I have, and found a bunch of different results and issues it could be, most likely seems to be a dash light or something since I just replaced the instrument cluster and it appears the coolant light is not functioning. But not sure since it seemed like a speed related issue.

 

I've just recently done quite a bit, I replaced the spark plugs, fuel injectors, alternator, belt, etc. In 2017 it looks like the whole top end was rebuilt and the ECM was replaced as well.

 

I had a 93 Buick LeSabre that had a Quad Driver Module fault. I didn't remember that it was code 26. I replaced the ECM with one from the salvage yard and it cured the problem.