kst8engineer

iTrader: (6)

Guys, I could use some help from anyone that's had experience with retrofitting a late model (LS-era) cluster into an older vehicle. For temporary use, I wired up the '99 Trans Am instrument clutster in my Chevelle until I get around to working the factory gauges over. I connected the necessary wires (at least the ones I thought were necessary), and I've had partial success...

The oil pressure gauge works, the volt meter works, and the backlighting on all the gauges works. For some reason, the speedo, tach, and coolant temp aren't working (nor is the odometer). I believe these three gauges all get their signal from the serial data wire, which I have connected. I can read vehicle speed, engine speed, and coolant temp via a laptop connected to the diagnostic port, so I know the signal is being sent from the PCM correctly. I measured the resistance from the serial data connection on the instrument cluster to the serial data wire on the diagnostic port, and the resistance is nearly nothing (maybe 0.1-0.2 ohms), so I'm confident I have a good connection on the serial data wire.

Other than the serial data wire, what else could prevent these gauges from reading? Maybe there's another necessary wire that I missed connecting.

kst8engineer

iTrader: (6)

Any thoughts? The MIL seems to be working, so that backs up the thought that the serial data connection is good.

Speartech

iTrader: (14)

MIL has nothing to do with serial data.

The serial data line controls fuel gauge, water temp gauge, tach.

Oil pressure, speedo/odo, and MIL are direct lines into cluster.