Has anyone come up with a neato way to replicate a Tech 1? I have the ability to scan (TTS Datamaster), but there are a lot of areas in the FSM that call for hooking up the Tech 1 and activating certain relays, IAC, etc. I am particularly interested in trouble shooting a DTC 28. My fans don't turn on anymore. Is there a way to replicate these steps without spending hundreds of dollars on a tech 1 or do people just skip over those steps assuming the answer is no or something?

 

The Tech 1 is a bi-directional device. You would need the software or to be more exact the control words that the car responds to via the bus. You would need the vocabulary to make it do things like close relays. It would be quite a software project and have never seen any of this information made accessible to the general public. As you know there several scanners that only display information on the bus. And some can flash the chip.

It's probably easier to get a Tech 1 and a mass storage cartage or cartages that would relate to what car you want to work on. I believe a Tech 2 will do the same and more but is much more expensive.

I don’t think there is a cheap way around the Tech 1 or it would be common knowledge already. The Tech 1 does a lot of stuff.

 

The bi-directional feature of the Tech 1 mentioned by Paul is just one reason I've always felt it is a bargain for C4 owners. Yes it costs more than a laptop cable or low end consumer grade scan tools, but it is far less expensive than a Tech 2.
Understand too that the Tech 1 can access all the other computers on the C4 such as CCM, ABS, FX3 etc., none of the software/laptop solutions or inexpensive scan tools can do that.

As you have already noticed troubleshooting your ECM issue the Tech 1 is used for many of the tests in the FSM, if you search other sections of the manual you will see is used in a similar fashion to diagnose CCM, ABS problems as well.
Prices on Tech 1's have dropped since they have been obsolete in dealerships for years, but they can still be very valuable to C4 owners who tackle their own repairs.

That said I will attempt to address your question as asked. Yes, it is possible to perform some of the tests the FSM calls for without having a Tech1, but it does require a comprehensive understanding of how the ECM controls the outputs in question as well as first rate skills using the wiring diagrams.

As an example I will point out that to activate the fans with the key in the "ON" position the Tech 1 is simply grounding the correct terminal on the fan relay just as the ECM would do. Look carefully at the wiring diagram and you will notice that the "control" wire for those relays on your 92 is dark green with a white tracer for fan #1 or dark blue with a white tracer for fan #2. You can use a jumper wire to ground at the relay or ECM to make the same check, but it is much more difficult and you must use great care to make sure you do not ground the wrong wire by mistake.

When you see smoke coming out of the ECM you can be sure at that point it will need a rebuild.

 

Well that is a good point. I spent a little more time looking at the wiring last night and I discovered that there have been some "improvements" made. The 12V line from the ignition has been jumpered to the heavy 12V constant from the battery. That cannot be good. The ignition line is protected by a 5A fuse, the battery by a 30A fuse. I think I have a toasted relay or QDM in the ECM as the circuit to activate the relay is now protect by 30A fuse instead of a 5A fuse. I probably had somewhere north of 5A going to my computer when it grounded the circuit and activated the fan. It also looks like there is a temperature switch between the two fans. Lets see if I can explain this in print, There is what appears to be an extra 2 wire temp sensor in my upper radiator hose where it T's off to the intake. The T has a ground wire soldered to it. One wire of the temp switch is jumpered to the BLU/WHT wire, the other is jumpered to the GRN/WHT wire. The switch appears to be open at cold. The only reason I can think of to add this (assuming the switch closes at hot) would be to turn the secondary fan on with the primary fan once the coolant reaches a certain temperature. In this way, when the switch is hot and closed and ECM grounds the primary fan, it also grounds the secondary fan. Maybe this would be done becuase the A/C was removed? I will have to go through the chart to be sure, but I see some potential to really mess up the ECM. Relays are new, I replaced them to "fix" the fans when I bought it, looks like in my ignorance I just passed the problem on down the line to the next weakest link.

This car is like a game of whackamole! @#$%@#$ PO

 

Sad that some moron hacked this car up, it is going to make your job way more difficult. Several of the circuits in the ECM are supposed to have "protection" to prevent damage due to shorted components or wiring, but there is no guarantee when someone has butchered the wiring as you indicate.
I would spend some time attempting to correct what you can before plugging in a rebuilt ECM. Sounds like you have good diagnostic skills and you will need them, best of luck.

 

Here is something that might help you out at this point rather than working in the dark. It's from the 94 but should be OK for the 93. You can see the fan control wires from the PCM (or ECM in your case)

Just to be clear how things should work, the ECM measures the coolant temperature from the sensor in the water pump which is the same temperature you see in your digital display. Then the ECM makes the decision when to turn on and cycle the fans on and off. Each control wire from each dedicated relay goes back to the ECM to get grounded to turn the fan on. The wire is the return (or bottom) from the relay coil.

**Found a second picture which was better but left both on anyway.

 

Using the FSM, I traced it back to a crappy connection. I went to the junkyard, found the relay harness off a '94 and I took the hackjob wiring completely out of my car and ran it per the FSM wiring diagram. Fans are operational again! Time to get back to replacing gaskets. Thanks for the help guys. I am thinking this hack was done to bypass the computer. That add in sensor grounds the ECM lines at a certain temperature. I guess the PO never thought of getting a tune?

 

Congrats on getting it sorted out!

 

Excellent.

The sucesss goes to your efforts and creativity.

 

Good work, congratulations! Always impressed with those who take the time to do the homework because that is the key.
Many come here looking for a quick fix or shortcut and most jobs require reading the book, doing the diagnosis and applying the basics.