There is a quick test to see if the ECM is actually running. While observing the CEL do a key-on, engine-off. The CEL should turn on briefly, blink off then turn on solid. Can repeat the test after a minimum of 10 seconds of key-off.
The blink off verifies that the ECM is actually running. Which is good. Note that it can take another minute after the CEL turns on (engine running) before the code is set. So if the blink off is there let the engine run longer before checking the codes.
If the CEL doesn't do the blink off can do this: access the ECM and remove the small cover. Pull the PROM out (the larger chip), then do a key-on, engine-off. The CEL light should flash or flicker rapidly. If it just turns on solid then the ECM is bad.
Note that the above tests should be done without anything plugged into the service port of the ECM. No PL, DS, and so on connected to the ECM.
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