Hi my check engine light came up on my 1992 Cadillac Deville. I got codes F48 which I believe is the A/C. I disconnected the sensor off the accumulator and forgot to connect it back and then I got code E90. What is E90 and how do I test and or replace it. I have had intermittent starting problems and now this check engine light is now on. When I say intermittent I mean it is off and on. When I try to start it their is no crank only dash lights come on that is it. An hour and a half later it starts. I try putting it in neutral to start it that does nothing I try it in park same thing nothing just dash lights. Thanks.
I can only answer some of your questions, but you find my answers helpful.
You intermittent starting is a very, very common problem caused by the GM junk known as VATS (Vehicle Anti Theft System) which was never designed to stop theft, but it sure stops many owners from driving their vehicles.
You can go to Cadillac and they will hit you about $800.00 for a new ignition lock and wiring harness, or you can take the vehicle to an alarm store and bypass the junk so you never have problems again and that will cost you about $60.00.
There are two very thin wires (similar to land line phone wires). One goes up the steering column and attaches to a contact in the front of the ignition lock cylinder. The other is attatched to another contact and runs down the column to the VATS module. When you insert the key, the resistor on the key hits both those contacts and completes the circuit. These wires break inside the plastic insulation and movement puts them back together. They cannot even be tested for the break with an ohm meter because as I said they go back together. I think if you tried tilting the column, you would find the engine might start because you are moving those wires.
The bypass is just inserting the correct resistor (1 of 14) under the dash in line eliminating the wires going up and down the column. I have fixed thousands of these and the system is junk!!!!Good thing I don't tell you my real feelings about VATS. lol
When I was at the dealer the common complaint was "Engine cranks at times." GM will not bypass. They will tell you it is because of security. The truth is that you are not paying them $800.00 for replacement of a lock that will ultimately fail again.
There is a 99.9 percent chance of that being the problem if the starter is good. Oh yeah, dealers have misdiagnosed and replaced a perfectly good starter, still having the same problem. I have even seen where a dealer replaced a perfectly goos alternator which has nothing to do with a starting problem. Of course there are no guaranties from the dealer and not only do you end up getting ripped on the ignition lock, but you have to pay for all the misdiagnosed components they replaced.
I have these complaints all the time on this site. Yet, just giving the advice I just did, I have diagnosed correctly the problem thousands of miles away from Dallas.
The check engine light i telling you the computer is in open loop and the engine is not running to optimum performance. Codes set the check engine light on.
As for the codes, if you want to fix this car now and forever, go to Ebay or Craigs and obtain a factory service manual. This will assist you in diagnosing your problems correctly. Otherwise you will just be chasing ghosts. This is the old OB I system and even the tech II scanner will not work to pin point the problem.
These codes cascade. A code 13 (o2) sensor can set of a code 34 (Map sensor) in turn set of a code in the 50s which is a computer problem. The chicken or egg theory. The manual has flow charts that will assist you in exactly what your problem is.
Check engine is an emissions problem and does not mean you can't drive the car. Your mileage and performance will suffer though.