The programmable read-only memory (PROM) chip in each ECU is not replaceable. Technician B says the PROM chip is the only serviceable part in the ECU. Who is correct?

The programmable read-only memory (PROM) chip in each ECU is not replaceable. Technician B says the PROM chip is the only serviceable part in the ECU. Who is correct?

• A. Technician A
• B. Technician B
• C. Both Technician A and Technician B
• D. Neither Technician A nor Technician B

Answer: (B)

The key idea here is which parts of an ECU you can actually service in the field. The PROM stores the ECU’s firmware, and in many automotive ECUs the rest of the circuitry is tightly integrated and not field-serviceable—often sealed or designed to be replaced only as a whole unit. Because of that, the PROM area is the part technicians focus on when attempting repairs or reprogramming, while other internal components aren’t typically serviced individually. So, in this context, the statement that the PROM is the only serviceable part aligns with how many field-service scenarios are handled, making that technician’s claim the most reasonable in terms of what can be serviced without swapping the entire ECU. If deeper hardware faults appear in non-serviceable parts, the usual remedy is to replace the entire ECU assembly.

The key idea here is which parts of an ECU you can actually service in the field. The PROM stores the ECU’s firmware, and in many automotive ECUs the rest of the circuitry is tightly integrated and not field-serviceable—often sealed or designed to be replaced only as a whole unit. Because of that, the PROM area is the part technicians focus on when attempting repairs or reprogramming, while other internal components aren’t typically serviced individually. So, in this context, the statement that the PROM is the only serviceable part aligns with how many field-service scenarios are handled, making that technician’s claim the most reasonable in terms of what can be serviced without swapping the entire ECU. If deeper hardware faults appear in non-serviceable parts, the usual remedy is to replace the entire ECU assembly.