timlash

2003 996 manual transmission Carera cabriolet - My tachometer stopped working and center message screen reports "Engine Fault", but otherwise the car runs fine. My ODB2 reader says the car does not report any fault codes. However the ODB2 reader does display engine RPM. Any tips on where to start looking for tachometer faults?

De Jeeper

Guessing u have a wiring issue between the dme and the guage cluster. The cps is obvioisly sending the signal to the dme because its running but its not reaching the dash or obd2 plug. Nowhere near my bently manual so cant help any further with the wiring.

timlash

Thanks for your reply! The ODB2 does report the engine RPM as the car runs, so some data is getting to the plug. It just doesn't report a fault. I'm not sure what dme (engine computer?) or cps (crank position sensor?) mean. I'll start looking at wiring harnesses I guess.

Mike Mullins

Remove the Dash Pod and see if one of the 3 connectors is loose. I want to say it's the Blue Connector on mine.

Freaked me out , ($$$$) but if the bail that holds the connector isn't set correctly each section can shut down.

If you haven't ever removed Pod I think the is some instructions at Renntech.org.

Be careful with Hazard switch.

De Jeeper

Then i agree with post above. Check your connection to the cluster.

Also yes dme, engine computer, cps is the crank position sensor. The cps generates the signal that the computer uses to determine rpm and motor position. Since the car is preforming correctly it points to the gauge connection.

timlash

Thanks for the advice! I'll look for the instructions to pull the gauge cluster.

timlash

Thanks for the confirmation. Getting instructions to pull the gauge cluster now.

Mike Mullins

hard to release

timlash

Solved! Nothing was wrong with my ECU or instrument cluster. The tachometer was just fine. It simply wasn't getting a signal to display. I have since learned that the tachometer gets its RPM signal from...the alternator! Four months after my original post, my alternator stopped working suddenly and completely. Drove home on battery and ordered a replacement. Two wires are connected to the alternator, a heavy positive voltage cable that feeds electrical current to the car, and a small sensor wire that feeds the tachometer engine RPM. Installing a new alternator brought the tach back to life and cleared all the warning/indicator lights. I've attached a picture of the dash (sorry for the glare) with the lights lit before total failure of the alternator. Cruise control, temp gauge and fuel gauge all worked fine despite the warning lights. Only the tachometer wasn't working. Once the alternator failed completely, every light on the dash lit up. Car still ran fine, of course, just drained the battery on the drive back home. Hope this can help someone else.



Green cruise control light, engine temp light and low fuel light all permanently on when my tachometer lost it's signal from the alternator. Cruise control, temp gauge and fuel gauge all worked fine despite the lights.

DBJoe996

Wow! Thanks for the update on what turned out to be the problem. Who would have thought the alternator provides the signal for the tach? I'm still not getting it. Wonder what happens to those who put on an underdrive pulley on the crank...