SLOPONY

I am swapping a 2001 chevy Silverado 2wd 4.3 v6 5speed, non AC truck over to a 5.3. The donor truck was a 2000 5.3 tahoe 4wd automatic with electronic shift 4wd with AC. I removed all the wires from the harness for the automatic transmission, and installed the ones from the v6 harness for the 5 speed. I have not modified any other harnesses aside from the Tahoe engine harness. I have verified the grounds. The bed is off, and tail light harness is not plugged in.

I do not have a consistent ground on pin 5 in the OBD2 port. The gauge cluster lights up the back lights, but does not power up warning lights, or gauge function, but if I apply ground through pin 5 with a power probe, it all works as it should.

The engine will not crank with the key, but will if I apply power through the correct pin of the starter relay, It will also run when I do this, and stay running until I turn off the key.

I also noticed that the third brake light is on when the key is on, but, the bed harness is not hooked up as the bed is still off.

I have deleted the following:

EGR, EVAP, rear 02 sensors, Power steering, Fuel pump, Fuel level, fuel tank pressure, ABS module is no longer in the truck. Fuel pump power wire is now being used as a trigger for an after market relay to power a bosch 044 inline pump, connected to an aftermarket fuel cell.

The ground on pin 5 of the obd2 port has ground with key off, and loses ground and shows 2-8 volts with the key on. When the key is turned off, the warning lights, and fuel level gauge will flicker until ground is applied to that pin, then they go off.

I am guessing that I have removed a wire from the PCM harness that I shouldn’t have, or I am missing a ground that I didn’t hook up on the engine harness. I have the two on the back of the block, drivers side, and passenger side, lower drivers side block under #3 cylinder, and the main ground of front passenger side of block. Also the ground on the frame behind the cab. I added star washers to the grounds to ensure a good contact, and all terminals do show ground when probed.

While removing the transmission wiring, I did notice a black with white tracer going to either the trans or transfer case that went back to the ground junction inside the harness. I did not hook this ground up to any thing, and left it cut back inside the harness.

Computer was reprogrammed, 5 speed files were added, EGR, EVAP, rear o2s were removed, vats was disabled.

Hopefully I have given you enough info to help point me in the right direction on this issue.

SLOPONY

UPDATE

No crank issue was a pain in the *** to find, and simple to fix. Under the clutch pedal area on the flood of the truck is a junction box. Green 4 wire connector for the clutch switch was loose, and not clicked in. Bumped it by accident while probing the clutch switch wires, and hitting the key, elbow grazed that plug, and it cranked. Snapped it all the way in, and POOF problem solved.

The ground source for pin 5 of the OBD2 connector was not something I was able to trace back through the harness, so a new ground was put to the chassis, and all seems to be well.

I took it for the a quick test drive on the start up tune. It won't idle, but it runs good, doesn't over heat, doesn't leak, and didn't catch on fire... so now its a few finish up items, and off to the dyno for final tuning.