I have done a swap to an LS motor using an FITech fuel injection system system. I had to keep the 2.8 ECU because some of the gauges are run thru the original 2.8 ECU. My problem is that when I removed all of the engine control wires from the 2.8 wiring harness, I mistakenly removed the temp sensor wires that go to the 2.8 ECU. When I found what I had done, I reconnected the yellow wire number 410 back to the ECU (Cavity C10 on C2 block). the other wire was a ground. After all a ground is a ground is a ground right? Well it was supposed to be connected to cavity D13 on C2 block, wire #452 which is the sensor ground. I think I may have damaged my 2.8 ECU by using a chassis ground. I have traced and ohmed the wires from the ECU plug to the temp sensor, changed the temp sensor and the gauge never reads anything. Have I missed something? Thoughts?


89 Firebird 5.3 LS with FiTech EFI

 

Yes, AFAIK, none of the sensors run through the stock 2.8l ECM. That ECM is about as dumb as it gets.

Nice Firebird, looks to be in good condition.

RBob.

 

The 2.8 is multi-port fuel injected. The temp sensor is connected to the ECM. otherwise how would the ECM know when the engine was up to operating temp to start leaning out the fuel mixture.

 

The ecm and dash use separate sensors.

 

There is a 1 wire temp switch that controls the coolant fan, but it wires directly to the coolant fan relay. That is the only other temp sensor I can find in the factory service manual wiring diagrams or on the 2.8 I pulled.

 

This may be from a from 3.1 car but they really didn't change. Note N5

 

Thank you aliceempire, you got me headed in the right direction. I had tunnel vision on the ECU. I just found what you posted in my shop manual and that led me to the C100 diagram and the schematic of the instrument cluster. now I have to figure out where I cut the dark green wire I need for the temp gauge so I can splice it back in to it.