Scanmaster not working again!

Today I looked into both the low fan relay and TCC systems.

My TCC solenoid is working properly, after verifying 12 VDC at the plug to the side of the tranny either 12vdc on or 12vdc off depending on the brake pedal switch, I took it for a test drive. I verified the solenoids operation by driving at a steady 50 MPH while slightly depressing the brake pedal. Just enough to activate the brake switch and not letting of the gas. I listened for the TCC unlocking which is verified by the PRM slight increasing....which i heard. After releasing the brake pedal the RPM's will drop. So this tells me that the system is working properly....right? And that the ECM is working properly...right?
 
As far as the tcc it sounds like it's working properly. The relay when 12v is supplied you can here it click, completing the circuit. But if the resistance is not anywhere from 0-2 ohms, that's an indicator of a failing relay. You might want to pm turbobob. I think he will be able to go more in depth.


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It sounds like your car is running so I don't know what would be "murdered" in the ECM. We are dealing with almost 30 year old electronics. I am wondering if there is electrical noise in the ECM corrupting the date stream to the ALDL. The Scanmaster may be seeing the stream as no data and shutting off? Have you tried a different scan tool?
 
v6turbo87 said:
It sounds like your car is running so I don't know what would be "murdered" in the ECM. We are dealing with almost 30 year old electronics. I am wondering if there is electrical noise in the ECM corrupting the date stream to the ALDL. The Scanmaster may be seeing the stream as no data and shutting off? Have you tried a different scan tool?
Click to expand...

whats 'murdered' is the driver chip in the ecm is frying ! ...what he damaged is the portion that controls the sm data, low fan and the tcc ..the rest of the ecm still functions
...its like loosing one channel output on a stereo. the rest of the stereo can work but theres something wrong with the speaker or wires to it that caused that channels amp to die .
he needs to find that problem or every ecm he puts to that car will be damaged ... basically 'murdered' by him because he didnt find the cause of the damage
 
So if he fried/murdered the driver chip how do you explain the fact that his TCC is still working?
 
pacecarta said:
whats 'murdered' is the driver chip in the ecm is frying ! ...what he damaged is the portion that controls the sm data, low fan and the tcc ..the rest of the ecm still functions
...its like loosing one channel output on a stereo. the rest of the stereo can work but theres something wrong with the speaker or wires to it that caused that channels amp to die .
he needs to find that problem or every ecm he puts to that car will be damaged ... basically 'murdered' by him because he didnt find the cause of the damage
Click to expand...


I agree! I need to find the problem.

I need to disclose this info...I don't know the history of this vehicle. I purchased about 10 months ago, put into storage, deployed...and now I'm back (in Alaska) and it's summertime! So I'm not familiar with this car or turbo Buicks/GN's in general.

Thus far, I believe I have ruled out the TCC. I've verified the functionality and operation is working as it should. Don't know what else I could check in regards to the TCC system.:unsure:

As far as the Low fan relay circuit, I feel I need to look deeper into this...only because
-I have aftermarket electric fan set up.
-I found wires cut to both the high and low fan relays
-The electrical fans turn on, but according to my temp gauge, they turn on at about 215 degrees until the temp is about 180 and then they turn off. They fan system will allow the temp to reach (IMO) a very high temperature before turning on. I feel they should turn on earlier.....right....???

I understand the "murdered" theory within the ECM and how only one channel can be effected while leaving the rest of the ECM alone. However, I don't understand how the TCC system is working but the data link (same channel) is not working. Wouldn't the bad channel prevent the TCC system from working?

I will chase the wires on my Stock fan system as well as the Aftermarket system and let ya know what I find.

Thanks again
 
that fan turn on temp is driven by the switch on the top of the manifold below the iac , thats your hi speed relay being turned on because the switch closes at approx 224*....
you dont have a low speed fan operation which is commanded by the ecmand depending on your chip the turnon couldvary , on tt chip ts around 168 turnon , stock was around 195
 
Last edited:
and your test show the tcc is locking and grounded and that pressing the brake pedal which kills the power to the tcc caused the tcc to disconnect ....it did not verify that the ecu is controlling the ground , it could be grounding at the ecm (all the time) or grounded by a switch somewhere in the car or even grounded inside the trans depending on whether it has a BRF harness in there
 
pacecarta said:
that fan turn on temp is driven by the switch on the top of the manifold below the iac , thats your hi speed relay being turned on because the switch closes at approx 224*....
you dont have a low speed fan operation which is commanded by the ecmand depending on your chip the turnon couldvary , on tt chip ts around 168 turnon , stock was around 195
Click to expand...


Thanks,

Well then, based off the temps you've mentioned I can say without a doubt that the "low temp" circuit is not being energized from the ECM.
 
pacecarta said:
and your test show the tcc is locking and grounded and that pressing the brake pedal which kills the power to the tcc caused the tcc to disconnect ....it did not verify that the ecu is controlling the ground , it could be grounding at the ecm (all the time) or grounded by a switch somewhere in the car or even grounded inside the trans depending on whether it has a BRF harness in there
Click to expand...


hmmmm....interesting.
 
Take an an ohm meter an monitor pin F of the ALDL to ground. If it is open on start up and shows a short under certain driving conditions it will prove if the ECM is making the ground for the circuit.
 
v6turbo87 said:
Take an an ohm meter an monitor pin F of the ALDL to ground. If it is open on start up and shows a short under certain driving conditions it will prove if the ECM is making the ground for the circuit.
Click to expand...


Thanks,

I spend the better afternoon chasing wires on the following circuits; low and high fan relay, delay fan, A/C fan clutch, coolant fans, ecm, and coolant temp switch. I didn't find anything abnormal. All reading were as the schematic shows.

But I did find the delay fan relay completely corroded... see pic.

I have a new ECM coming in tomorrow and a couple of relays. I hope this works!
 

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I hope that solves your problem. My low fan relay was bad and I also have a new ecm on order. ( warranty ). When I put my last ecm in I thought I solved my scanmaster problem. 2 hours later it stopped work again. So I hope with the new relay and ecm, my problem gets solved


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That is common for the fan delay relay. It is up to you if you want to replace it as it is not needed and causes more problems than it is worth.
The only things being driven by the quad driver that is being "murdered" is the low speed fan relay, the TCC solinoid, and the serial data line to the ALDL. I would leave the fan relay and the TCC solinoid unplugged when you try the new ECM. Then see if the Scanmaster works.
 
I will try that v6turbo87. Makes sense. And the relay you are telling me to leave unplugged is the middle one on the driver fender right? Just do I'm on the same page as you.


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v6turbo87 said:
No the middle one is the high speed relay the other small one is the low speed.
Click to expand...

This might be true on some cars....but it wasn't on mine. My 'low' speed relay is the middle one. The best way to tell which one is the 'low' speed is by looking for two solid green wires going to the relay plug.
 
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