Chrysler Repair: 1996lhs chrsyler when the lights come on the motor is erractic, diagnostic capability, chrsyler

Question
i have a used 1996 LHS CHRYSLER THE SPEEDOMETER GETS ERRACTIC WHEN I TURN ON THE HEAD LIGHTS. TYHANKS

Answer
Hi Indigo,
The quickest way to a solution is to make use of the built-in self diagnostic capability of the engine controller. Reading out the engine controller memory for fault codes is the first step. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for several engines and we can look up the possibilities of what is wrong based upon what fault codes you show. There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair. Let me know the codes and which engine is in the car and I can give you some direction.
Roland