What does general motors trouble code 26 mean?

Question

I have an old 89 bonneville with a leaking egr valve i can use a pray bottle when the engine is running spray the egr valve & see bubbles coming from the vale itself does that determine it is weak & needs replaced or is the channel to the intake stopped up not allowing exhaust gas 2 pass through to the intake expensive 2 replace want to make sure of problem before i spend 2 bills & same problem has no fault codes for egr & has low power when it is cold warms up does fine once in a while low power when it's warm is this due to egr only fault code new is code 26 not sure what it is telling me that problem is .

I have an old 89 bonneville with a leaking egr valve i can use a spray bottle when the engine is running spray the egr valve & see bubbles coming from the valve itself does that determine it is weak & needs replaced or is the channel to the intake stopped up not allowing exhaust gas 2 pass through to the intake exspensive 2 replace want to make sure of problem before i spend 2 bills & same problem has no fault codes for egr & has low power when it is cold warms up does fine once in a while low power when it's warm is this due to egr. only fault code new is code 26 not sure what it is telling me that problem is .

I have an old 89 bonneville with a leaking egr valve i can use a spray bottle when the engine is running spray the egr valve & see bubbles coming from the valve itself does that determine it is weak & needs replaced or is the channel to the intake stopped up not allowing exhaust gas 2 pass through to the intake exspensive 2 replace want to make sure of problem before i spend 2 bills & same problem has no fault codes for egr & has low power when it is cold warms up does fine once in a while low power when it's warm is this due to egr. only fault code new is code 26 not sure what it is telling me that problem is .

Answer 1

I own a shop, and from what I can tell; I would say you have a bad (Electronic Control Module) ECM. If you are getting this code on an Oldsmobile or Buick, then this is what the problem is. Looking at the code book, it gives this code in many places, but these are GM codes in which cover many different vehicles, and the first code there is for Quad Driver Circuit, and probably doesn't apply to yours. What does jump out at me is the ECM failure on your vehicle type. The others will be as follows: (1) Transaxel gear switch circuit, (2) EVAP purge solenoid circuit (vin P 5.7 liter engine), (3) TPS circuit shorted, and (3) Idle speed control (ISC) motor/throttle switch circuit shorted. If I were to bet on this one, I would bet you have a bad computer. To be fully certain, you must eliminate the others, or have the dealer run the diagnostics on it for you for a fee. You must use the symptoms the engine is doing, and incorporate that into all the different codes you get from the computer, and match the code that best describes your symptoms. If you are concerned about the EGR, then make a plate to temporarily block the EGR off completely, and I think you will find you still have the problem. Yes, a leaking EGR will cause a idle, and a running problem if they leak, but this is due to it sticking in the open position, and sucking air into the engine, not blowing bubbles out. The other components can be checked with a meter to determine if they have signal, ground, and voltage (if present) all the time. Understanding these parameters can be difficult at least, and the best way I have found to test the component is with a sensor tester, or ohms meter. You will need a Haynes Repair Manual for your vehicle in order to follow the procedures for testing each sensor/component. It has been my experience that; anytime a bunch of codes are present, then just replace the computer, because its highly unlikely several sensors will go bad at one time. The single most cause for any code will a power or ground problem. Clean all the battery cables, and any and all cables or wires that attach from the engine to the firewall. Many problems can be resolved by just doing this. Many times a computer will give false codes when it doesn't get the correct amount of voltage, or a good ground is not established between the battery, engine, and the body of the vehicle.
Glad to help out, Good Luck!!!

Answer 2

It's a quad driver code. There are four quad drivers in the PCM that are used to activate solenoids. They use these to eliminate any big currents into the PCM which would fry the computer. Code 26 is usually associated with another code if it is an EGR problem. I think the other codes would be 63, 64, or 65 depending on which solenoid in the EGR was faulty. These are pretty easy to check, so that's what I'd do first. Turn ignition on, but don't start motor. Test power to the EGR valve connector. Pink wire, I think. If you have power, that's about all you can do from this standpoint. The other connections run back to the computer which grounds the solenoid when it is determined to do so. If you have an ohmmeter, check the resistances of the solenoids. If you have an open one, the valve has had it. What I used to do is use the GM scanner to command an EGR solenoid on while the motor was idling. You can feel the motor start to misfire when the valve is turned on. If you have a wiring diagram, you can locate these grounding wires back to the PCM and do this manually. This is a pretty simple circuit, so if you don't understand how to diagnose this take it into a shop with a good scanner and it would take them about ten minutes to run this test. The code 26 could mean something else is wrong as well. This code also takes into consideration some of the transmission solenoids as well as the TCC solenoid. Spraying something onto the EGR does not tell me anything as it is usuallly hot, so you tell me what you're looking at there.

Answer 3

General Motors Trouble Codes

Answer 4

DTC 26 refers to a quad driver module fault. The quad driver is a "safety valve" for the ECM controlled circuits. The quad driver controls up to 4 circuits. There are multiple quad drivers in the ECM. The QDM shuts down a shorted circuit to prevent high current flow from damaging the ECM.

So the DTC 26 will isolate the problem to 1 QDM. You will need a repair manual with electrical diagrams and DTC flow charts to determine which of the circuits controlled by that QDM are failing. Usually DTC 26 refers to the Torque Converter Clutch solenoid and related circuit.
Most likely you have a shorted TCC solenoid or the harness connected to it, The solenoid is internal in the transmission accessible from the side cover.

I will assume this is a 3800 V6 w/ 4T440 / 440 T4 transmission with the digital (3 solenoid valves) EGR valve.

The bubbles from your EGR valve can indicate a leaking EGR valve and may not set a code. However it can also indicate excessive back pressure in the exhaust, hence a possible faulty catalytic converter (broken substrate) along with intermittent loss of power and other symptoms.

Answer 5

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GM negotiated ridiculous retirement contracts in the seventies to prevent strong-arm labor from striking. At the time it seemed a good idea but leave it to GM to never look beyond their own nose (or in this case, beyond the retirement of the execs who would not have to worry about it later). GM now is so strapped for cash due to funding retirement accounts they are struggling to turn a profit. In their defence, Japan has a national retirement system in place so their car makers do not have to deal with these woes as does GM, Ford and Chrysler. This coupled with decades of sub-standard products have left them wasted.

Answer 6

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Answer 7

QUAD DRIVER MODULE.