1993 TrasSport 3.8L Quad Driver Codes 26 and 56

[tinkering]

Originally Posted by LMP

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.

My mistake, it looks like they use the 8th digit. In that case, I too have a VIN L.

[Jeffrv]

The PCM ground, as well, and many sensors, should be located on a ground stud under the ignition module. C heck there to see if any wires have broken or are corroded

[Blue Bowtie]

35Ω is good for a "12V" solenoid for purge, TCC, and many of the other things the ECM would be controlling. Using Ohm's Law, that would translate to well under 2A at the 15V where the system normally operates. The quad driver sinking output transistors are commonly rated at 4A continuous, with heat sinks designed for that power dissipation.

[tinkering]

Originally Posted by Jeffrv

The PCM ground, as well, and many sensors, should be located on a ground stud under the ignition module. C heck there to see if any wires have broken or are corroded

The ignition module is under (part of) the coil pack. Is the ground post connected to the underside of the coil pack unit? Is it easy to see or do you need to poke around under there with a mirror?

[Jeffrv]

Yes, it is buried under the IM, you will need a mirror and flashlight to get a good look. If I remember, you will need a 15 MM deep socket to get it out

[tinkering]

Originally Posted by Jeffrv

Yes, it is buried under the IM, you will need a mirror and flashlight to get a good look. If I remember, you will need a 15 MM deep socket to get it out

Excellent! I will have a look

I came across a page that listed all the ground connections but can't remember where.
I also need to go back and check to see what the other units are that both the Quad Drivers control. I can't remember where I saw that either. It might be in this thread otherwise in a manual.

[tinkering]

Originally Posted by 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

1. I need to focus on the major G200 ground that you mentioned in post #38.

2. I forgot to do the 'flex test' when doing my continuity checks from the sensors to the engine side of the C110 and C111 30 pin connector blocks.
I had to plug everything back together so I could move the TS so I basically have to start over with this one.

3. I need to focus on the 'ground post' under the IM as in post #47

4. I need to locate the rest of the grounds.
Patience is a virtue. Thanks to you and the others for your virtuosity

[tinkering]

MY OFFICIAL GM 2 BOOK SHOP MANUAL ARRIVED TODAY!!!

[tinkering]

Still hard at this one but getting no further. My new manual is giving me a bunch more ideas though.
Is the GM 'Tech 1' Scan Tool of any significant value to have? Where and how much is it?
Does a GM OBD I to OBD II adapter cord work (eBay)? I have a decent OBD II scanner and it would be handy to use it for my OBD I TSport.

Other things to look at for DTC 26 besides the Purge Solenoid, are the Puller Fan Relay, TCC Solenoids Connector, TCC Brake Switch. Any others?

Other things to consider for DTC 56 besides the EGR Valve, are TCC, improper shifting (there is that harsh shift when transaxel gears back up from kickdown passing at 60-75 mph). Could this do it? Any other related components to DTC 56?

I was checking 'Pin Drag' on the PCM connectors C1 and C2 and they are not uniform; I am wondering if that could be part of the trouble. What's the best tool to free the pin connectors from the socketsif that needs to be done?

[LMP]

Originally Posted by tinkering

Other things to consider for DTC 56...

Wiring continuity is still my prime suspect. I remember having tested continuity to the EGR valve right from the pins B1 , K3 at C111 and E2 at C110. WIth KEY ON and EGR plug connected, 12V is fed to all EGR coils and returns through the coils and wiring to all 3 contacts so you should measure 12V on each .
ABout transmission, if it shifts to all gears 1,2,3,4 then it is cleared from DTC 56 . If TCC applies then it is clear from DTC 26.

Tech 1 scanner is proprietary to GM...not on the market in as much as I know...

[tinkering]

Originally Posted by LMP

Wiring continuity is still my prime suspect. I remember having tested continuity to the EGR valve right from the pins B1 , K3 at C111 and E2 at C110. WIth KEY ON and EGR plug connected, 12V is fed to all EGR coils and returns through the coils and wiring to all 3 contacts so you should measure 12V on each .
ABout transmission, if it shifts to all gears 1,2,3,4 then it is cleared from DTC 56 . If TCC applies then it is clear from DTC 26.

Tech 1 scanner is proprietary to GM...not on the market in as much as I know...

I will check the EGR wiring again using a volt meter as you described. I will be sure to do a vigorous 'flex test' simultaneously.

Last road test I still had the MIL going out intermittently around 85 to 110 kph. I don't seem to get that when I rev the engine at a stand still, maybe up to 4000 rpm. Does that indicate anything to you?

It seems to always shift through all 4 gears. What indicator do I look for that the clutch is actually energizing, and it's not all just fluid coupling that's taking place? At what point does the clutch energize?

[LMP]

Originally Posted by tinkering

Last road test I still had the MIL going out intermittently around 85 to 110 kph. I don't seem to get that when I rev the engine at a stand still, maybe up to 4000 rpm. Does that indicate anything to you?...? At what point does the clutch energize?

THe egr valveS apply one after another or idependently under specific loads. At some point, the "faulty" EGR valve is not energised...hence the fault is not detected, hence no MIL. WHen conditions are such that THIS valve is tentativelky energised..and it does not, then you have the MIL. I have lived this condition too.
THe torque converter clutch can apply in 3rd and 4th gear. It applies only under light load and once applied in 4th gear, the RPM at 100 km/h will drop to 1600-1700. Without the TCC, rpm in same conditions will be over 2000.

[tinkering]

Originally Posted by LMP

THe egr valveS apply one after another or idependently under specific loads. At some point, the "faulty" EGR valve is not energised...hence the fault is not detected, hence no MIL. WHen conditions are such that THIS valve is tentativelky energised..and it does not, then you have the MIL. I have lived this condition too.
THe torque converter clutch can apply in 3rd and 4th gear. It applies only under light load and once applied in 4th gear, the RPM at 100 km/h will drop to 1600-1700. Without the TCC, rpm in same conditions will be over 2000.

I'm just getting back to this after being busy with other things. I can't blame it on the summer because we didn't have one🌞
I see a replacement EGR valve for $80 on Amazon.ca. I am tempted to throw it at the TransSport. Maybe there is a problem with the original and the wreckers EGR valves. I have spent so much time tracing and testing continuity all over the place without finding the culprit, maybe it's just the valve. I can go back to rechecking wires if the new valve doesn't pay off. Does this sound feasible to you, or is it just a feable attempt by a nearly defeated victim?🏳️

[tinkering]

Originally Posted by tinkering

I'm just getting back to this after being busy with other things. I can't blame it on the summer because we didn't have one🌞
I see a replacement EGR valve for $80 on Amazon.ca. I am tempted to throw it at the TransSport. Maybe there is a problem with the original and the wreckers EGR valves. I have spent so much time tracing and testing continuity all over the place without finding the culprit, maybe it's just the valve. I can go back to rechecking wires if the new valve doesn't pay off. Does this sound feasible to you, or is it just a feable attempt by a nearly defeated victim?🏳️

I changed out the EGR valve with the new one, Standard brand. The light is still on but now it idles very rough when it slows down to idle rpm. Crumb

[tinkering]

Originally Posted by tinkering

I changed out the EGR valve with the new one, Standard brand. The light is still on but now it idles very rough when it slows down to idle rpm. Crumb

The new gasket wasn't quite right. There was 3 gaskets with the new valve but none of them are correct.
I put the old gasket back on with tbe new valve. It's idling down correctly again but that light is still on. I have to check the codes again; maybe there is a different code keeping the light on now. Otherwise I have to go back amd do the testing LMP mentioned.