I have a 1998 Pontiac Transport the SES light came on revealed a code
440 emissions problem. Replaced the gas cap, reset the ECM and the code went out. 100 miles later the SES light came back on steady all the time after the car cranks, even after the battery has been disconnected it still remains on. The engines runs normal as always. The kicker is that putting a ECM reader on the ALDC shows that there is no power at the connector. Nothing has been modified in the car other than replacing the stock radio with an aftermarket radio ("professionally" installed) Does the radio have an electronic connection to the ECM or the ALDC?Any clues appreciated...