1993 TrasSport 3.8L Quad Driver Codes 26 and 56

[tinkering]

The purge valve readings are on the previous page. Please be sure to see them. Thanks

As for the temp sending units (CTSs):
*The one with the single contact (I think it controls the gauge) is 2810 ohms at 68F. The chart says they should be 3400 ohms at 70F.
*The double contact unit (I think might work with the ECM in controling the purge valve activation) reads 3040 ohms at 68F.
Both readings are somewhat low but considering a 10% +/- tolerance (brings it to 3060 ohms at 70F) are they good enough?
Is checking it at 70F good enough or do I need to check them at operating temperatures of 190, 200 etc.?

[LMP]

THis one from the transport shop manual. Same values
http://www.avigex.ca/xport/thermistor.jpg
IN fact, these thermistors are practially standard and used all over the car industry. My Kia Sorento , wife's Suzuki SX4....all the same
Values change rapidly across the temperature range, so minor differences at a specific temperature are irrelevant. ANd what you say about the purge solenoid valve is OK.
YOu can see both temp sensors on these diagrams, 1 for ECM, one for instrument panel

[tinkering]

I checked the thermistors (CTSs) at round 40F too. I filled a sour cream tub with ice and water; cut a hole in the lid and threaded the CTS in so it reaches into the water.
I took the readings at around 35F-40F. They all seem to be changing with the temps, within reason as per the temp/resistance chart. So I am going out to put things back together.
If codes 26 and 56 remain I am thinking it is a wire or connector problem (I've done everything else I can think of) with the purge valve and EGR valve.
I'll get back.
thanks

[tinkering]

Went onto the highway test. The check engine light went out for a few minutes. I thought I had success but it started going on and off after awhile. Now it appears to be staying on again.
I picked up a new code, #44 oxygen sensor; exhaust appears to be lean.
... but back to the main focus, codes 26, and 56.
Code 26: I am swapping out the carbon can with a wrecker unit.
Code 56: I am going to clean the wrecker EGR unit. If that doesn't help I am going to put the old EGR back in. The next time to the wreckers I will pick up another EGR, one that looks newer.
Question: Are the Quad Drivers in the ECM or the PROM? I expect they are a part of the ECM. I am likely going to have to check the wires from the ECM to the EGR, and from the ECM to the purge valve but I only have a manual that covers 1991-1992 3.1L.
Do you have the chart/schematic I need to trace the wires out on my 1993 3.8L?
I can look to see if the reference voltage is arriving from the ECM, and stuff like that.

[Blue Bowtie]

The quad drivers are hardware in the ECM, not the PROM or MEMCAL pack. A quad driver is an array of solid state output switches (four of them in a package) used to operate moderate load devices, such as the EGR solenoid, EVAP, indicator lights, transmission solenoids, etc. The ECM monitors them to see if they have overloads or open circuits. When the ECM detects a fault it sets a code. That can mean a failed driver in the ECM, or an open or shorted circuit or device connected to a driver.

[tinkering]

Originally Posted by Blue Bowtie

The quad drivers are hardware in the ECM, not the PROM or MEMCAL pack. A quad driver is an array of solid state output switches (four of them in a package) used to operate moderate load devices, such as the EGR solenoid, EVAP, indicator lights, transmission solenoids, etc. The ECM monitors them to see if they have overloads or open circuits. When the ECM detects a fault it sets a code. That can mean a failed driver in the ECM, or an open or shorted circuit or device connected to a driver.

I'm barking up the right tree
I need a schematic or diagram that indicates wire colors, pin locations in the ECM connectors, and reference voltages so I can start narrowing things down. I can check ref voltage at the sensors and solenoids to check for short to ground or opens but need to know where to find them at the junction blocks, the ECM and it's connectors etc.. My manual doesn't cover 1993 TSport with the 3.8L engine. I assume the wiring will be different enough on the '91-'92 3.1L to let me down?
If the Qdrivers monitor the indicator lights, might a bad coolant temp gauge trip a code (or is that independant of the ECM circuits)? The temp gauge needle rides on 1/4 max; I've changed out that coolant temperature sensor, and I've replaced the thermostat with a 195F. It made no diff to the gauge; the needle never reaches up past the 1/4 position.
I found this link on YouTube. It is just about all I need except I would like a diagram to reference along with it.

Watch "How to test an electronic EGR valve (GM P1406 case study)" on YouTube
https://youtu.be/te_kapz-fj4
This guy ScannerDanner has a bunch of diagnostic videos on his YouTube channel, and a forum. He is teaming with info; talks a litte fast but it sinks in when reviewed. Fun to watch too.

Does the 93 TSport with 3.8L have an EVAP Vent Solenoid as well as the purge valve solenoid, or does one do the same job as the other?

[LMP]

Wire colors here, as in post #7
www.avigex.ca/xport/dtc26.jpg
www.avigex.ca/xport/dtc55.jpg
www.avigex.ca/xport/dtc56.jpg
looking for the pin ....
www.avigex.ca/xport/c111.jpg
www.avigex.ca/xport/c111b.jpg
www.avigex.ca/xport/IMG_0126.JPG
and the complete EVAP section
www.avigex.ca/xport/EVAP.pdf
about code 44, that is what made my TS unserviceable: it was an open O2 sensor heater .
see my thread here: http://www.automotiveforums.com/vbul....php?t=1151502
It came with a DTC13. It made the fuel burn spike up . I have bought a new O2 sensor but not installed yet....I use another car now.

[Jeffrv]

You seem to find the sensors are pretty well in spec, so it would seem your thoughts about wiring issues would be the most likely cause. Two problem areas I have found in the past in my 95 TS are poor grounds, especially the major G200 ground located behind the drivers kick panel. As well, I have found engine vibration has caused intermittent internal breaks in wiring harness within the first 8 inches or so of the 2 engine to body 30 pin connectors. The body side is fixed, the engine side flexes, leading to intermittents. trace the wire from connector to device, and flex the harness as you test for continuity. It is a pain, I have had 2 circuits fail like this, and tracking down took some time
Good luck

[LMP]

Originally Posted by Jeffrv

... I have found engine vibration has caused intermittent internal breaks in wiring harness within the first 8 inches or so of the 2 engine to body 30 pin connectors.

I confirm this.

[tinkering]

Originally Posted by LMP

I confirm this.

Do you have a schematic of the other 30 pin connector too? C110 I think. The one that is on more in front, above the carbon can.

[LMP]

Coming....
www.avigex.ca/xport/c110.jpg
www.avigex.ca/xport/c110a.jpg

[tinkering]

Originally Posted by LMP

Coming....
www.avigex.ca/xport/c110.jpg
www.avigex.ca/xport/c110a.jpg

Thanks, these diagrams helped me immensely, even though they are for a
'VIN L' and mine is a 'VIN U'.

I did continuity checks on all the wires of the EGR and Canister Purge Solenoid, from the units right on through the C111 and C110 connectors to the 3 ECM connectors under the dash. I was disappointed to find zero opens.

With the ECM connectors still plugged in I was getting strange readings on what I think were the ground wires in the harnesses; some at 5 ohms, some at 25 ohms; it left me puzzled. Could there be a bad ground strap somewhere causing this, or...?

I need to go back and check continuity on the ground wires through to the ECM connectors, with the ECM connectors disconnected (I can't remember if I did that or not.) If there are no funny reading when unplugged then it might be resistance being noticed in the circuitry of the ECM.

I need to locate all the ground straps and re-fasten them.
This is dragging on but that is what wiring mysteries do.

I found a GM manual on eBay for $50 so I ordered it... waiting for shipment from USA.

I bought a download manual from eManualsonline.com but it was not the vehicle specific GM OEM manual that they advertised, so I have one now that covers a bunch of years but I'm not happy with that substitute they forced on me without even a partial refund. Be wary of that company.

[LMP]

Originally Posted by tinkering

Thanks, these diagrams helped me immensely, even though they are for a
'VIN L' and mine is a 'VIN U'....

NOt sure why yours would be a VIN U ...in my book, VIN D is for the 3.1, VIN L for the 3.8. I know though that the platform for these models was known as the U body....

[tinkering]

Originally Posted by LMP

NOt sure why yours would be a VIN U ...in my book, VIN D is for the 3.1, VIN L for the 3.8. I know though that the platform for these models was known as the U body....

Which digit do you use again?
My 5th is a U, my 8th is an L.

[LMP]

Originally Posted by tinkering

Which digit do you use again?
My 5th is a U, my 8th is an L.

No reference to my serial number 1GMDU06L......

VIN D and VIN L are used in the shop manual ; VIN L for 3.8 and VIN D for 3.1 . AS I said, this body is known as U so possibly in the serial number U refers to the body, L to the engine type. I had not noticed before.