Diagnostic Scanners

Have a 1990 Geo Metro 3cyc with air with abt. 85,000 miles on it.
Have had problems in the past with rough idle and missing but after changing spark pluges, rotor, and dist. cap and also cleaning the egr and pvc valves the car runs much better. I have never had problems with the engine light coming on but want to be able to read the computer for problems at a later date if the problem reoccurs or a new one develops. How many codes is the 1990 Geo able to show? Also, is there an inexpensive diagnostic scanner available for this year? Thanks.

I own a '96 so I'm unsure of the details, but the search function should show you threads that discuss inserting a fuse into a special empty socket in the fusebox and counting how many times the SES/CEL light flashes. A particular flash-count = corresponding code.

OBD-II scanners are only useful for '96 and younger vehicles.

Yeah, you don't need a scanner for your car. It is what is known as OBDI (on board diagnostic) 19xx-1995ish for fuel injected vehicles. Technicians of this era did have scanners available to them but different manufacturers had different DLC's (data link connector) which made it a big pain in the rear and required a wall full of adapters for different cars. Under your dash, where the fuses are located you will see a fuse slot that has a raised edge around it, higher than the surrounding fuses - look carefully. Place a spare fuse in that slot with the ignition off - amp rating is irrelevant. Sit in the driver's seat with a pen and paper, turn on the ignition. It takes a little getting used to, but the check engine light will flash and pause. eg. flash-pause-flash-flash = 12. For more than one code stored it will look something like, flash-pause-flash-flash--long pause--flash-flash-pause-flash for two codes 12 and 21 respectively. The computer will repeat the series of flashes and pauses once all the stored codes have been displayed. You can then look-up these codes in a chiltons or haynes manual or perhaps online.

-mechanicmatt

Thank you very much for the information. I went to Krangens yesterday and looked at a scanner. It did the same thing as what you say the car will do. You saved me some bucks. Thanks again.

Jim