ScanMaster stopped working

[DeltaBravo]

Hello all...

ScanMaster stopped working while driving. I was about a mile down the road and it just went blank. I turned around went back home and pulled her back in the garage.

Since then, I've been searching on this forum and found some interesting reads on the same subject, but recently I'm experiencing some difficultly with this website. Some days, this site won't even load...other days like today, the 'search' engine for the forums doesn't work and keeps coming up with an error.

So...I'm lost and don't know where to start. I've double checked all three wires from the ScanMaster; ground is grounded...power is receiving 12vdc from a ignition source...the third that plugs into the diagnostic port is still in the correct one (orange wire, top row, second from the left).

Today, I checked continuity from the diagnostic port (orange wire) to the ECM (orange wire)...it's good. I read the VDC at both the diagnostic port and right out of the ECM and it's only about 850 mvdc...less than 1 VDC. is that normal? I think I remember reading something about 4-5vdc....dunno?

I haven't been able to verify the ScanMaster itself nor the ECM. However, I can get the ScanMaster to illuminate momentarily when I turn the ignition on...it reads 2.1 but after a few seconds it gone and nothing follows.

Any advise...
Thanks,

 

[TurboBob]

that is indicative of no data. Its usually caused by the driver in the ECM failing. But the drivers don't die, they get murdered.

the low speed fan relay and TCC solenoid are both run by the same driver device in the ECM. I would look for a bad low speed fan relay or TCC solenoid, and then you will need the ECM repaired.

I am 99.9% confident the Scanmaster is ok.

Bob

 

[DeltaBravo]

Well that sucks...ECM repair. Who does that?

 

[DeltaBravo]

TurboBob,

I would like to do some trouble shooting today but what would I look for.?

Low fan relay-Resistance of the coil inside the relay?....what would a 'good' reading be?

TCC-not sure but this sounds like I need to drop the tranny pan...dunno?

Thanks

 

[DeltaBravo]

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

TCC solenoid is working properly, after verifying 12 VDC at the plug to the side of the tranny is either on/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 LOW fan relay. I read the resistance across the coil and it's "seemed" good...it think it was around 300 ohms or something. Either way, my Fan does not come on until about 210 degrees. At what temperature will the "low" fan relay receive the signal from the ECM to turn on the fan?

Thanks

 

[TurboBob]

low fan turns on based on the chip programming. stock chip is 195 I think. most of the aftermarket chips are in the 160 to 175 range.

300 ohms sounds a little high actually. I just measured a generic relay here and it is 75 ohms on the coil.

Bob

 

[DeltaBravo]

Thanks TurboDave,

I will double check the resistance of my relay. I did check both the low and high relays just to compare and they read the same...again I don't remember the accurate reading, I just remember them both being the same. I've attached a pic of my chip.

As you mentioned in many post, the ECM gets 'murdered'. I'm hoping I can figure out what might have done this. Because I don't want to go through the time and money of a rebuilt ECM just to have it murdered again.

Anymore insight/testing on the Low coolant circuit would be helpful.

Damon

 

[DeltaBravo]

Update...problem fixed.

After meticulously reading wires in all the systems that relate to TCC and cooling, I didn't find anything wrong except for what was discovered the first time, I'll explain later. However, I did find my 'delay' relay was completely corroded... so it has been removed and the plugs were taped up and secured. Both the high and low relays had a high resistance in comparison to the new ones...so they were removed and replaced with good ones.

The first thing I noticed after this initially occurred were a few wire cut at both the high and low relays. The green with yellow stripe was cut to the high fan relay and both the solid green wires were cut to the low relay. These were repaired and then I made sure all the wires had good continuity and not grounded out when they shouldn't be.

The only thing I cannot (or just don't know how) check is the TCC solenoid in the transmission, so for now...it's unplugged.

Installed new/remanded ECU and started it up! ScanMaster is working as advertised!

And....they best thing is she stays sooooooooo much cooler. Stays around 170....instead of hitting 220 and then the fans come on until about 190 and then back up to 220 and back to 190...so on and so on.

Thanks you for all the help.

 

[TurboDave]

Update...problem fixed.

After meticulously reading wires in all the systems that relate to TCC and cooling, I didn't find anything wrong except for what was discovered the first time, I'll explain later. However, I did find my 'delay' relay was completely corroded... so it has been removed and the plugs were taped up and secured. Both the high and low relays had a high resistance in comparison to the new ones...so they were removed and replaced with good ones.

The first thing I noticed after this initially occurred were a few wire cut at both the high and low relays. The green with yellow stripe was cut to the high fan relay and both the solid green wires were cut to the low relay. These were repaired and then I made sure all the wires had good continuity and not grounded out when they shouldn't be.

The only thing I cannot (or just don't know how) check is the TCC solenoid in the transmission, so for now...it's unplugged.

Installed new/remanded ECU and started it up! ScanMaster is working as advertised!

And....they best thing is she stays sooooooooo much cooler. Stays around 170....instead of hitting 220 and then the fans come on until about 190 and then back up to 220 and back to 190...so on and so on.

Thanks you for all the help.

Here's some wiring help.

 

[DeltaBravo]

Thanks TurboDave,

That's the very same source I used to trouble shoot.