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Qdm 26 cooling fans come on and stay on and voltage drops

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QDM stands for Quad Driver Module.The QDM is located inside the PCM (Powertrain Control Module),or the vehicle's computer.Think of a circuit breaker,like the electrical breaker box in your home.If a circuit,any circuit becomes overloaded,the breaker "clicks" and shuts off power to the circuit.It resets itself after the load is gone,or the key has been cycled.I have never seen an actual QDM go bad.To repair this problem,the coolant temp sensor will need to be checked for proper operation.This is done with a scan tool that can access data.If the PCM is seeing a proper reading from the temp sensor,then it's on to another area,possibly the fan relays.If the relay is bad,it can melt internally and either shut off voltage,or allow continuos voltage.Check the relays.The wiring to and from the fan is also another area to be checked,but check the simple stuff first.Other than those areas,PCM command would need to be monitored.Good luck.

Posted on Jul 18, 2008

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I have an 05rendezvous,need to locate switches for cooling system,fans aren't co ming on & now I'm going to need a new radiator,cuz plastic broke.But it broke before fans gave out.Which I changed stat


The engine cooling fan system is controlled by the body control module (BCM) and the powertrain control module (PCM) or engine control module (ECM). The BCM performs the calculations as to how long, when and what speed the cooling fans should turn on. The BCM then sends a class 2 message to the PCM/ECM to engage the cooling fan relays. If there is a malfunction with the BCM, the PCM/ECM will control the engine cooling fans independently. The engine cooling system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the PCM/ECM to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood accessory wiring junction block. The ground path is provided at G100.
During low speed operation, the PCM/ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 2 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM/ECM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM/ECM supplies a ground path for the cooling fan 3 or S/P relay and the cooling fan 2 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The BCM and PCM/ECM command Low Speed Fans on under the following conditions:
?€¢
Engine coolant temperature exceeds approximately 106?°C (223?°F).


?€¢
A/C refrigerant pressure exceeds 1 310 kPa (190 psi).


?€¢
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140?°C (284?°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The BCM and PCM/ECM command High Speed Fans on under the following conditions:
?€¢
Engine coolant temperature reaches 110?°C (230?°F).


?€¢
A/C refrigerant pressure exceeds 1 655 kPa (240 psi).


?€¢
When certain DTCs set.


The three relays are located in the under hood fuse / relay box ! You need to have it checked for DTC'S -diagnostic trouble codes ! An you need a GM Tech 2 scan tool !
This diagnostic procedure supports the following DTCs:
?€¢
DTC P0480 Cooling Fan 1 Relay Control Circuit


?€¢
DTC P0481 Cooling Fan 2 and 3 or S/P Relay Control Circuit


?€¢
DTC P0691 Cooling Fan 1 Relay Control Circuit Low Voltage


?€¢
DTC P0692 Cooling Fan 1 Relay Control Circuit High Voltage


?€¢
DTC P0693 Cooling Fan 2 and 3 or S/P Relay Control Circuit Low Voltage


?€¢
DTC P0694 Cooling Fan 2 and 3 or S/P Relay Control Circuit High Voltage


  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Fans Low Speed ON and OFF.
Do the low speed engine cooling fans turn ON and OFF with each command?
Go to Step 3
Go to Step 4

3

Important:: A 3 second delay occurs before the powertrain control module (PCM)/engine control module (ECM) changes the cooling fan speed.
With a scan tool, command the Fans High Speed ON and OFF.
Do the high speed engine cooling fans turn ON and OFF with each command?

Aug 08, 2015 | Cars & Trucks

1 Answer

It's a 1995 Saturn sl the clutch on ac compressor kicks on with direct power the engine fan also changed relays still get the code 26 quad drive modal need some help


This info is from 1998 Saturn Sl , my service info doesn't go to 95 . It's the same except for code numbers , My info is P0xxx #'s . The quad driver is part of the ECM - engine computer !
Here is a description from Saturn service info .
A quad driver module (QDM) is an electronic switch which completes a ground circuit when switching ON. The QDM independently controls 4 separate outputs. A load is connected between battery voltage and the QDM allowing the QDM driver to control the output. Each QDM has fault detection logic which compares QDM driver input and output voltages. The logic expects to measure less than 3 volts when the QDM driver is ON and greater than 7 volts when OFF. The QDM has only one fault line that will detect a fault on any of the 4 outputs. The scan tool can be used to cycle the outputs ON or OFF. The scan tool can also perform an automated test which can isolate the faulty circuit.
The quad drive it self may be bad , GM had a problem with these !
Did you check fuse's ?
Conditions for Setting the DTC
DTC P01650 and/or P1651 will set if:
?€¢
There is an open, short to ground or short to voltage on any of the QDM output circuits


?€¢
MIL (SERVICE ENGINE SOON) telltale circuit


?€¢
Upshift lamp circuit


?€¢
Cooling fan relay circuit


?€¢
A/C relay circuit


?€¢
Fault detected for 5 seconds for DTC P1651. Fault detected for 20 seconds for DTC P1650.

Important: The QDM circuit is continuously checked when the engine is running.

May 18, 2015 | 1995 Saturn Sl

1 Answer

Where is the radiator fan switch located on a 2002 oldsmobile intrigue


The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood accessory wiring junction block. The ground path is provided at G113. The relays are located in the underhood fuse / relay box .
So ,what's the problem Paul , car overheating ? Fans not working ?
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the right cooling fan. The ground path for the right cooling fan is through the cooling fan 2 relay and the left cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the right cooling fan. At the same time the cooling fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the left cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The PCM commands Low Speed Fans on under the following conditions:
?€¢
Engine coolant temperature exceeds approximately 106?°C (223?°F).


?€¢
When the A/C is requested and the ambient temperature is more than 50?°C (122?°F).


?€¢
A/C refrigerant pressure exceeds 1310 kPa (190 psi).


?€¢
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140?°C (284?°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:
?€¢
Engine coolant temperature reaches 110?°C (230?°F).


?€¢
A/C refrigerant pressure exceeds 1655 kPa (240 psi).


?€¢
When certain DTCs set.



So

May 11, 2015 | Oldsmobile Cars & Trucks

1 Answer

Buick 92 code 26


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code 26 is .... Quad Driver Module (QDM A) error

Oct 11, 2013 | 1992 Buick Regal

1 Answer

Probable cause on a 1992 buick code 26 and 42 show up can some one help me please


code 26 is .... Quad Driver (QDM) "A" Fault
code 42 is ..... Electronic Spark Timing (EST) Circuit

Oct 11, 2013 | 1992 Buick Regal

1 Answer

I have a 91 Buick Century limited 3.3L with a 3300 engine. I ran a diagnostic scan of which produced the two-digit codes 12, 26, and 27, and In attempting to look up these codes, I found a website on...


DTC 26 and 27 refers to a QDM (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 or 27 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.

Also, keep in mind the single most cause for any code will be 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.

Hope this helps; also keep in mind that your feedback is important and I will appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Nov 28, 2011 | 1991 Buick Century

1 Answer

My car is overheating while idling, once im driving the temperature drops back to normal, i realized that the fans are not running at all, what connections should i check? could this be the cooling fan...


turn your a/c on which should send signal to cooling fans to operate, regardless of engine temperature. check for voltage on cooling fan wires. if voltage is not present check relays and fuses located passenger side front of vehicle under hood. if voltage is present, then i would replace the cooling fans

Feb 21, 2011 | 1995 Oldsmobile Aurora

1 Answer

Code26and27prolemona1990buickcentury ineedtoknowwhatcode26quaddrivermodule(a)operatesordrivessoicantraceoutmycodefaultandgetmycarsmogedthankyou


Code 26 is caused by the quad driver module receiving an incorrect voltage.
Check your battery charge/voltage is sufficient - a dodgy battery can mess with this. Otherwise check the QDM and wiring for faults.
I'm reasonably sure your code 27 doesn't specifically refer to another problem in that model
Hope this helps, Sherwin

Dec 12, 2009 | 1990 Buick Century

1 Answer

Code 26 what does it mean


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.
Keep in mind the single most cause for any code will be 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!!!

Oct 28, 2009 | 1989 Pontiac Bonneville

1 Answer

AC and Cooling fan will not come on


the older s-series had quad drviers,,,check the qdm and a/c anf fan relay under the hood,,,,if good between the trans pan at the top of trans and the cylinder head there is a little black box with a connector replace that and see if it helps, those older ones are tricky,they have some stuff the other years never had

Oct 08, 2009 | 1991 Saturn SL1

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