NJFBOA - Home of New Jersey's Camaros and Firebirds - View Single Post - Car acting crazy, throwing codes P1642 and P1642

Pampered-Z · 01-02-2009, 08:40 AM

Sounds like two unrelated problems. The codes for the fans should not result in the car missing or stalling.

Do you happen to have a manual fan switch installed? They can cause the ECM to throw codes? If not, check the fuse (25 amp) and them check the relays. You can first try swapping the relay for the fog lamps with a fan relay, see if both/either work. If not you should probably break out the volt meter and check the current and resistance going to the relays.

Since the tach doesn't always work and it stalls I'd start at the ICM and work back. make sure you have good contact with the coil/ICM/Head/grounds. The tach is driven off ICM, it's the wire with the 1"x1" box that is taped to the harness. Make sure that wiring harness is connected properly, no loose wires or corrosion. Also make sure you have a good ground. There should be a ground strap from the frame as well as 2-3 other wires that connected to the bolt that attaches the ICM to the head.

01-02-2009, 08:40 AM	#6
Pampered-Z Sliderule / Moderator Join Date: Oct 2004 Location: Catawissa PA Posts: 2,294 iTrader: (1)	Sounds like two unrelated problems. The codes for the fans should not result in the car missing or stalling. Do you happen to have a manual fan switch installed? They can cause the ECM to throw codes? If not, check the fuse (25 amp) and them check the relays. You can first try swapping the relay for the fog lamps with a fan relay, see if both/either work. If not you should probably break out the volt meter and check the current and resistance going to the relays. Since the tach doesn't always work and it stalls I'd start at the ICM and work back. make sure you have good contact with the coil/ICM/Head/grounds. The tach is driven off ICM, it's the wire with the 1"x1" box that is taped to the harness. Make sure that wiring harness is connected properly, no loose wires or corrosion. Also make sure you have a good ground. There should be a ground strap from the frame as well as 2-3 other wires that connected to the bolt that attaches the ICM to the head. __________________ 93Z M6 Black: The 385 Lives! Supercharged, 3-core front mount intercooler, GTP heads, 3:73's, Street twin clutch, Jethot Longtubes, Mufflex 4" catback/spintech, S+W cage, Spohn Suspenion, Yada Yada Yada 1) Build it 2) Race it 3) Break it 4) Repeat!!!