You can check a 1993 Oldsmobile Delta 88 Royal's Electronic Control Module the same you would an engine diagnostic. The ECM is the "brain" in the Delta's diagnostic system. The module runs a series of checks and routines; once a malfunction is detected, the ECM labels it with a code. The Delta uses General Motor's pre-1996 first-generation On-Board Diagnostic system, and some of GM's OBD-I codes deal directly with the ECM and the system itself. Retrieving the codes is a relatively simple process that requires a paper clip.
Look up GM's flash codes. You have two options, depending on the amount of cash you are willing to part with. GM's flash codes can be found online for free. They are also listed in many of Haynes' repair manual. A manual, whether from Haynes or from Chilton, might be a wise investment, as you will not only have access to the codes, but also detailed repair instructions.
Read through the flash code definitions. Note all the coding definitions that deal with the ECM and its related functions. For example, GM code 86 refers to a digital or analog error within the ECM.
Open the Delta 88 driver's side door. Place your resources on top of the dashboard. Place your key into the Delta's ignition, but leave the key unturned.
Find the Delta's Assembly Line Data Link connector. The ALDL is a 12 pin-receiving hub that connects to the ECM. It will be directly under the Delta 88's steering wheel.
Straighten out a metal paper clip. Bend the clip into a capital "U" shape.
Connect the "B" and "A" slots on the ALDL with the U-shaped paper clip. Both slots are on the ALDL's top row, next to each other and to the far right, at the end.
Turn the key in the Delta's ignition. Pick up a pen and paper and wait for the check engine light to convey fault codes via flashing lights.
Count the number of flashes and write them down. The two digit codes will be conveyed with long and short flashes. For example, code 12 will be one long flash followed by two shorter flashes. There will be a pause between code sets. Code 12 is always at the beginning of this process. It is meaningless, and you need not write it down or look it up.
Consult the resources you left atop the dash. Look specifically for the flash codes you noted earlier. If none of the codes you recorded deal with the ECM, then your Delta's computer is operational. If you do find ECM-related faults, you have a few options. The ECM itself may need to be rewired. It also may need to be replaced. If this is the case, drive the Delta to a General Motors-approved technician. Since the Delta is an older vehicle, finding a replacement ECM may be more difficult then replacing a contemporary car's computer module.
