swapped out 7747 for 8746(EBL).

Geeky Bill added ability to use IAT on unused pin #21(84 vette harness). I added the lead from IAT to that pin on ECU. click A-OK. grounded IAT at the harness near IAT location(black). IGN on. got CE? engine on and IAT not sending signal per Learn VE. went to MALF codes and unchecked 23 and 25. No CE but still not sending signal. used the coolant/iat tables in stock EBL table.

what am i missing? how to diagnose? used new IAT for 92 Chev Camaro.

 

At room temperature the IAT sensor will be about 3K ohm (3000 ohm). Use a DVM and at the ECM measure between ground and the IAT lead to pin #21. Should be reading close to 3K ohm. If the sensor is hotter then the resistance will be lower, colder will be higher.

Can also measure the sensor itself.

If all that checks out, double check with Bill for the proper ECM pin.

RBob.

 

RBob says: Use a DVM and at the ECM measure between ground and the IAT lead to pin #21. Should be reading close to 3K ohm.

is that with ignition off ?

 

Yes, ignition off. Both the IAT & CTS sensors are resistive. As the temperature changes the sensor resistance changes. For testing you just need to measure the resistance of the sensor. Doing it at the ECM verifies the sensor and the wiring.

RBob.