I once bought a new 1991 Mazda B2600i pickup truck to haul materials for a remodeling project. The engine was controlled by a microprocessor-controlled ECM (Engine Control Module), which was a somewhat new technology at the time.
The truck was extremely reliable for about 10 years and then started to have starting/rough-running problems. After ruling out other sources for these problems, I decided that the problem was with the ECM. Replacement ECMs are generally $200 to $300 or so, but the local Mazda dealership wanted $1,400. Apparently, so many 1991 Mazda 2600i ECMs had failed that replacement ECMs were in short supply and commanded a premium price.
With nothing to lose, I opened up the ECM and immediately noticed that one of the electrolytic capacitors had failed and burst open. I replaced the obviously failed electrolytic capacitor and the other electrolytic capacitors in the ECU with extended-temperature-range electrolytic capacitors.
Apparently, early ECMs used normal-temperature-range electrolytic capacitors to save a few cents. Given that ECMs are typically closed boxes with components that can generate considerable heat in an environment that can get quite warm (think desert) and cold (think Alaska), this may not have been the best design choice.
In the end, I used a couple dollars worth of parts to repair the ECM and avoided paying $1,400 for a new one. And, after 22 years, the truck is still reliably hauling materials for remodeling projects.
This entry was submitted by David Moberly and edited by Jennifer Campbell.
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