1999 cadillac sedan deville 4.6 northstar check gas cap is on instrument cluster i scanned it and iget po1 and po3 any sugestions will be helpuful

Their not sending the computer out

Their are sending the instrument cluster out for repair

Get one from a salvage yard,I wouldn't spend that kind
of money

If you are refering to the Engine Coolant Temperature (ECT) sensor,it is located on the right rear of the engine below the exhaust gas recirculation (EGR) valve.

HINT: If your Deville is equipped with the analog instrument cluster and the temperature gauge is working, or if you have the digital instrument cluster and the driver information center (DIC) has been diplaying messages telling you that the engine is hot, the problem with your engine cooling fans is NOT the sensor.

SOUND LIKE FUEL PUMP GOING BAD.BUT CHECK THE EVAP CHARCOAL CANISTER FILTER IF GAS SOAKED REPLACE IT REPLACE GAS CAP MAKE SURE GAS CAP IS THE PRESSURE VACUUM TYPE.ALSO CHECK VACUUM PURGE VALVE VACUUM HOSE TO CARBURETOR AND CHECK VACUUM HOSE TO CHARCOAL CANISTER FOR BLOCKAGE RESTRICTION OR BROKEN AND MISSING.

Assuming you have the Northstar engine

P0440 - Evaporative Emission (EVAP) System leak, poss gas cap not tight or left off

only 4t60e transmissions work if its a 4.9l . only 4t80e work with the cadillac northstar 4.6l

It sounds like the problem is your dash cluster itself. you should be able to find another dash cluster for an 88 DeVille in almost any junk yard.

you need to figure out if your missing spark at the plgs,or check fuel pressure at fuel rail,you'll need at least 55psi of fuel pressure,but if you have had no luck spraying the throttle body,your probably missing spark

it most likely has a 4.6 liter V8 in it