no tach output

[steve40]

i got a 99 ls1 pcm running a 6.0 in a 97 (lt1) style firebird. the tach has work previously. just swapped in a 99 pcm to see how it compares to the 01 one for the transmission.

anyways everything is working cept for the tach. the scan tool does see rpm, just nothing to the dash

any ideas? not really sure where to look. the rest of the dash does work. i do have to do a case relearn, would that affect the tach?

[1meangto]

No that shouldn't effect anything. Theres a setting in system for tach output if I remember correctly. Why didn't you just reflash the pcm instead of swapping them? Check your connectors on the computer make sure no pins are missing or bent or pushed out. I can't remember if the tach has a fuse it may. It's in system>tach>parameters. Your values should be tacho pulses hi 6, tacho pulses low 6, yes enabled.

[steve40]

i wanted to try the 99 operating system.

my settings are 3, 3 and yes. i have a lt1 dash cause the car is a 97. so i believe you have to set the tach to read as a 4 cylinder to read correctly

[1meangto]

Ahh yes overlooked that. What settings did you have in it before you switched the pcm. I guess switch the pcm's back and see if the tach works would be the easiest check. Why didn't you just reflash the other pcm with a 99 os? I guess I've never done a lt1 car swap so I'm not sure.

[steve40]

so i hooked up my other pcm...tach works fine....put the 99 back in.....the tach lifts up when you turn the key and starts to read when cranking, once the motor starts its back to 0.

i have the same settings under the tach area for both tunes

also to flash the new operating system, do you just go to flash and program pcm op sys and cal?

thanks

[1meangto]

I just had a bad 01 pcm so it kinda sounds you have the same problem. For a NEW OS look at the tutorial. Flash the 99 pcm with the 01 cals and see if the tach works would be another way to test this.