ZoomZoom

Looking at a 2000 Z28 and it has a couple issues that I wanted to get some insight on before pulling the trigger.

First, the security light is always on, but he says the car runs & drives fine. What am I looking at as a likely fix? Hopefully, just the cheap VATS bypass box.

Second, it's throwing code P1860. He says he replaced the TCC solenoid as the converter was unlocking at highway speeds. That fixed that problem, but he's had the CE light on for that code since then. What are the most likely culprits for this?

Injuneer

The security system is monitored and controlled by the body control module. Codes can be read by putting the BCM in diagnostic mode, and flashing the codes on the SECURITY light. Sort of involved procedure.

You can download a copy of the 2000 factory service manual here:

LINK: 4TH GEN SERVICE MANUALS; 82-02 PARTS DIAG; 99-02 WIRING DIAG - Fourth Generation (1993 - 2002) - Firebird Nation

Putting the BCM in diagnostic mode starts in Volume 3 of 3, Part 1 of 2, page 8-534.

Logic diagram for troubleshooting "SECURITY light on, engine starts" is in Volume 3 of 3, Part 2 of 2, page 8-696.

P1860 sets when the PCM commands the TCC PWM solenoid on (90% PWM) and the voltage on the circuit remains near battery voltage for 5 seconds, or the PCM commands the TCC PWM solenoid off (0% PWM) and the circuit remains low (~0V) for 5 seconds. The PCM only turns off the MIL light after three consecutive trips without the problem recurring.

Again, factory manual, Volume 3 of 3, Part 1 of 2, page 7-245.

ZoomZoom

Thank you. Very helpful post. Does anyone happen to have pictures of their VATS bypass install?

GaryDoug

I have a temporary rig in my car's toolkit, for the day when it's needed. Here is a photo that also shows the resistor(s) inside. Normally you would just splice them into the wires going to the BCM.

ZoomZoom

Security light seems to be gone, but CE light came back after I cleared it.

ZoomZoom

VATS bypass got rid of the security light, but P1860 still present. Even though it was already done, I think I might just replace the PWM solenoid again & see if the light goes out.

Is this the only part that I should replace? Also, does anyone have the part#?

Also, what about the solenoid starting at step #4 in this guy's thread? Should I replace that as well? If so, cutting wires on the one in there & using butt connectors to install the new one ok?
http://www.fullsizechevy.com/forum/g...-write-up.html

GaryDoug

Here is what I would do first: Measure the resistance from the ENG CTRL fuse ( with battery disconnected, bridge the fuse socket pins with a paper clip and connect the meter lead to the clip) in one of the underhood boxes and connector C2 pin 2 of the pcm. If it measures 10-15 Ohms (per the factory F-car service manual), the pcm may be defective. Then wiggle the transmission connector around while watching the meter. If the meter reading varies a lot, the connector and/or wire may be bad. If the reading doesn't change, remove the pan and the TCC PWM solenoid and test it directly as above. If it measures ok, the 2 pin connector at the solenoid may be bad. If it measures bad, replace the solenoid.

In your second reference, this guy is replacing the TCC solenoid also, but you don't need to do that since the code is only for the TCC PWM solenoid.

ZoomZoom

Are you saying test the ENG CTRL fuse & C2 on the PCM separately or bridge them together & then test? Since they are at opposite ends of the engine bay, I'm assuming you mean separately. By "transmission connector" do you mean the wire @ C2 or something else?

GaryDoug

No, measure them together for resistance (battery disconnected). Normally we would check at the transmission's connector but that is inaccessible to measure.
The transmission connector is just that, the only one on the transmission. You would have to reach up into the tunnel to wiggle the cable.
So, you would connect the meter to the fuse somehow and to the pcm connector (unplugged), measure the resistance between those two, then wiggle the cable while watching the meter. You may need two people to do that unless you have meter wire extensions.

ZoomZoom

Apparently, I'm doing something wrong because I got no reading at all on my multi-meter. I can wire a stereo, but this kind of wiring troubleshooting is not my strong suit lol.

GaryDoug

The code indicates an open or shorted circuit where you measured. If you did it correctly, you got an open circuit indication (no change when you connect the meter leads). That would verify the code. It's possible the solenoid is open circuit but that may not be the case. One of the connectors or one of the wires to the solenoid may be defective. Did you try wiggling the cable at the transmission connector to see if the meter reading changed?
You may just have to drop the pan and check the solenoid directly if you can't see any problem elsewhere. Too bad you can't get to the trans connector better.

ZoomZoom

I think I am just going to drop the pan & see what happens.

ZoomZoom

I guess the PWM solenoid the PO put in was defective in some way. I replaced it again & no more P1860.