jdperk-86elco

Hey guys, I have been fighting this cruise control issue and just recently using EFILive to scan the inputs I found out the TCC brake switch input is not changing and the cruise is locked out. I traced it to the TCC brake switch input to the PCM where I have 12V coming from my NC brake switch and when the brake pedal is applied it should go to 0 (zero), however with the brake applied with the switch open there remains 10.4Vdc there all the time using a DMV. I cut my splice point and with the car running I still have 10.4Vdc on the PCM side purple wire which I think is going to pin 33.

It is a single wire and the only probable causes I can think of are three:

• A single strand of wire is poking into the purple wire from another wire causeing the voltage reading.
• A pin is bent in the PCM connector.
• The PCM pin single output is bad showing HIGH all the time with the 10.4Vdc

If the single pin output is bad can it be repaired, or will I have to get a new PCM.

RFERG43

Are you saying that pin 33 is an INPUT to the PCM? If so take a 1K ohm resistor and connect it from the OPEN wire going to the PCM to ground and see if it pulls the voltage down to zero. A simple drawing might help to explain the ckt you have.

jdperk-86elco

Yes this is the TCC Brake switch input for Torque converter lockup when the brake pedal is applied. I am not sure how the TCC works but I am guessing my PCM is compensating for this input not working.

I have a 28Vdc test light and it will not light it dimmly so I am guessing it is low current. I need to build a 12VDC test light and try it again.

Even if a 1K ohm resistor was able to pull it down if it is a bad input to the PCM it still wouldn't work, would it?

RFERG43

If a 1 K ohm resistor pulls the voltage down to zero it means the PCM input hasn't failed high causing the voltage you are seeing.

jimmyblue

iTrader: (11)

Test the switch itself and examine its mounting, see
if it is being actuated at all. Unplugged from the main
harness with an ohmmeter across its connector pins,
should show you what you need to know.

jdperk-86elco

The TCC brake switch is NC sending 12V to the PCM and when the brake is applied it opens removing the 12v or goes to 0V. The PCM side is a constant 10.4V all the time. When it was connected to the brake switch I could see it switch from 12V to 10.4V when the brake was applied. I verified the brake switch and wiring is correct. So car side wiring and brake switch is good.

I havn't had time this weekend to take it all apart. So my first plan of action is to trace the single purple wire and verify it is going to the correct input. If it is then I will try the 1K resistor.

When the brake switch was connected to the PCM EFILive showed the TCC brake input "Applied", now applied would mean brake applied and 0V input where the NC switch would send a constant 12V. So one would think it would show "Released" with the 12V on the pin constant or the 10.4V constant.

RFERG43

I'm not suggesting you are wrong, but it is highly unusual for any electronic device to have an input "open" unless it has an internal pull down resistor. Electronic devices don't like floating inputs. When you try the 1K pulldown resistor see what EFILive says. If the resistor doesn't pull the input to ground see if it pulls it lower tahn 10.5 volts. Normally and input to a device is either high (+12v) or low (ground). Do you have an actual schematic of the circuit?

jdperk-86elco

Guys,

I think I found the problem but I need to confirm. I traced the purple TCC Brake switch wire to the PCM blue connector pin 34. Should this input be connected to pin 33? The PCM is 2002 PCM I think?

Looking at the top for pin assignments I see different versions and it appears that blue connector pin 34 changes for different years.

Ok, so if I do need to switch this pin what tool do I need and where can I purchase one? For that matter where can I also purchase pins and a crimp tool for future additions?

James

jdperk-86elco

Guys,

The final fix was to move the TCC Brake Switch purple wire from pin 34 to pin 33. It was an honest mistake on the harness builder, I am just glad it was something simple.

I was able to see all things switch properly using EFILive. Thanks to Paul of EFI who gave me a new file that openned up the cruise control inputs so I could see them switch and help me troubleshoot it properly.

John at SpearTech has been patient with me trying to solve this cruise not working issue. His support with answering my questions was great.

Now to start seeing what I can tweak with EFILive. One of the first things will be to reset my Tach to read properly.

Problem solved!