crytical point

I am pulling codes off a 90 buick centry and I only got a code 26 but can't find what that means ANYWHERE. Can someone help my find out what this code stands for.

Vader

Quad driver circuit - Within the ECM.

Most ECM controlled devices are either solenoids or relays. Typically, solenoids are used for a circuit when the current draw is 0.75 amps or less, and relays are used in a circuit when the normal current draw is expected to exceed 0.75 amps. GM uses quad driver circuits inside the ECM to control the outputs to these devices. So quad drivers (QD) are integrated circuits inside the ECM that it uses to close or open the circuit path to ground, turning the device on or off. Depending on the make and model year GM vehicles use different variations of quad drivers.

* Early (CCC and TBI) Quad drivers (QDR)
Are permanently damaged if a device or its circuit shorts, no added circuit protection.
* Revised Quad drivers II
Temporarily shut down and then reset if a device or its circuit shorts.
* Later Quad driver Modules (QDM)
Temporarily shut down, sets a fault code, and then resets if a device or its circuit shorts.

Most quad driver circuit faults are due to a short in a device or its circuit (wiring/connectors). However at times a device or circuit that is open will set a quad driver fault code. Each quad driver can control up to four devices, thus, the name. Circuit diagrams would be used to determine which devices the quad driver at fault is intended to control.

Before simply replacing an ECM, always isolate the problem device or circuit. Replace the defective device or repair the circuit, and retest.

A wiring diagram would list all circuit numbers, the wire colors, and connector terminal numbers. The important thing is that each device and circuit is tested, found to be good or repaired as necessary. The proper test on these circuits would be, with key off disconnect all ECM connectors, then with an amp meter set on the 10 amp scale connected to the control side of the circuit at the ECM connector and to ground turn the key on and check that the device turns on. With the device turned on, the meter should read 0.75 amps or less. Run this test for at least five minutes to make sure the device isn’t overheating and shorting. The TCC solenoid cannot be tested in this manner in a vehicle that has a normally open third gear switch inside the transmission. A scanner thru an extended road test best checks the TCC circuit.

A normally operating device and its circuit will have at least 20 ohms of resistance and can be checked with an ohmmeter. This will only indicate if the circuit or device is open or shorted, but will not place the device in operation. If the suspect device is failing due to heating after being in use for a period of time the fault will not be found with a resistance test.

With proper test equipment and procedures it is reasonably easy to determine what circuit or device is causing a quad driver fault. You will need a multimeter and it would better to use one with at least a 10 amp current scale and is fused. The higher current rating will be beneficial when testing these and other vehicle systems.