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Summary: Electronic modules RARELY fail "all on their own" "due to age" or whatever. In the vast majority of cases an input or output to the module gets shorted to power or ground and either paralyzes or fries the module. Swapping modules, in a car OR a motorcycle is a better recipe for frying TWO modules than it is for diagnosing or repairing the original module failure. (IMHO, of course).
Backstory: Warren's 2009 Heritage Softtail recently began running so poorly as to be unrideable. It had to be towed to Arrowhead HD for repairs, under warranty. A SENIOR technician there, "Matt," following a printed or online diagnostic tree reported seeing some sort of false problem with the 02 sensors (details unknown), and the next step in the tree stated "REPLACE ECM."
Having diagnosed / dealt with failed / paralyzed modules extensively in the automotive world, I was unsatisfied with this diagnosis and repair. I believe the replacement module will (likely) fail for the SAME (albeit unknown) REASONS as the original one, probably within days or weeks. So I'm going on record here so I can claim a great big "I told you so!" if the replacement ECM fails, and ..eat a bunch of crow if it doesn't.
I'm not slamming HD, Arrowhead HD, or their tech, but I believe a LOT of techs with less electronics experience than myself will indeed "blindly" follow a diagnostic tree that may or may NOT be correct, and stuff in a new module instead of doing what I would do.
If you don't take the time and effort to figure out why the FIRST one failed, the SECOND one will likely go the same way, UNLESS it truly was an "old age" heat or vibration related failures, which are rarer then hen's teeth.
(In my automotive career I can count on one hand how many modules of ALL varieties I EVER saw that "simply failed" and didn't have an external cause, like some input shorted to power, or output shorted to ground out of dozens or hundreds of modules I was tasked to diagnose/replace. )
Caveat: An ECM input/output with an INTERMITTENT short is gonna be DARNED HARD to diagnose!
So how do you diagnose the CAUSE;
You take a multimeter and check every single input and output to the module for reasonableness. At least look for 12V or ground where it SHOULD NOT BE, for exmaple an ECM inputs that is say, expecting a 0-5V signal (made up example) out of an 02 sensor, potentiometer, rheostat, temperature sensor, etc. Or an output that has continuity to ground that should instead show some resistance.
Far too often in the automotive world what techs will do, when a module, anything from an engine ECM to an ABS controller is paralyzed, fails to respond to the scan tool, doesn't do it's job, is go to the dealership (or a junkyard), or borrow a "known good" unit out of another vehicle, and plug it into a problem vehicle. Modules today are often $500 and up...
As I said above, this is an absolutely fantastic way to FRY a second module, and if it's a "known good" loaner, thereby disabling a SECOND vehicle.
Techs who simply don't have extensive electronic backgrounds are EXPECTED, and REIMBURSED BY WARRANTY to follow the factory supplied diagnostic tree.
That doesn't mean the tree is correct. Or complete.
Nor does a tech have to be a real electronics GURU to check ECM inputs/outputs for reasonableness. Anyone who can use a meter properly can measure voltages, resistances, current, and check continuity. They just know it NEEDS TO BE DONE before calling a module, ANY module "bad" or stuffing a brand new one in, especially when it costs hundreds of dollars.
It goes a LOT faster when you have a helper who can read a schematic so one guy can probe inputs/outputs CALLED OUT by the guy reading the schematic. Counting pins and getting onto the right line is always a challenge with todays miniature connectors/pins.
Complicating Warren's repair is that his tuner is electronically "keyed" to his ECM, so ECM replacement is even more complex, and a SECOND FAILURE will add even more grief to the repair. (And weeks of delay as the tuner is sent back to the factory AGAIN to be re-keyed)
When I say "module" it doesn't have to be an "engine ccontrol module" it could be something as simple as an ignition "module." Basically ANY 'black box" with transistors inside, that has inputs, outputs, and 12V and ground power inputs. When a module, ANY module fails, the cause is USUALLY OUTSIDE of the module itself.
I'll report back in a few weeks on whether Warren's ECM truly did die "of old age." (rare) and its replacement was correct, or if now he's looking at SECOND module replacement.
Hopefully this little treatise will save those of you doing your OWN diagnosis and repairs from getting to buy TWO instead of one replacement modules, as they tend to be the most expensive parts on a bike/car anymore.
Questions?
Backstory: Warren's 2009 Heritage Softtail recently began running so poorly as to be unrideable. It had to be towed to Arrowhead HD for repairs, under warranty. A SENIOR technician there, "Matt," following a printed or online diagnostic tree reported seeing some sort of false problem with the 02 sensors (details unknown), and the next step in the tree stated "REPLACE ECM."
Having diagnosed / dealt with failed / paralyzed modules extensively in the automotive world, I was unsatisfied with this diagnosis and repair. I believe the replacement module will (likely) fail for the SAME (albeit unknown) REASONS as the original one, probably within days or weeks. So I'm going on record here so I can claim a great big "I told you so!" if the replacement ECM fails, and ..eat a bunch of crow if it doesn't.
I'm not slamming HD, Arrowhead HD, or their tech, but I believe a LOT of techs with less electronics experience than myself will indeed "blindly" follow a diagnostic tree that may or may NOT be correct, and stuff in a new module instead of doing what I would do.
If you don't take the time and effort to figure out why the FIRST one failed, the SECOND one will likely go the same way, UNLESS it truly was an "old age" heat or vibration related failures, which are rarer then hen's teeth.
(In my automotive career I can count on one hand how many modules of ALL varieties I EVER saw that "simply failed" and didn't have an external cause, like some input shorted to power, or output shorted to ground out of dozens or hundreds of modules I was tasked to diagnose/replace. )
Caveat: An ECM input/output with an INTERMITTENT short is gonna be DARNED HARD to diagnose!
So how do you diagnose the CAUSE;
You take a multimeter and check every single input and output to the module for reasonableness. At least look for 12V or ground where it SHOULD NOT BE, for exmaple an ECM inputs that is say, expecting a 0-5V signal (made up example) out of an 02 sensor, potentiometer, rheostat, temperature sensor, etc. Or an output that has continuity to ground that should instead show some resistance.
Far too often in the automotive world what techs will do, when a module, anything from an engine ECM to an ABS controller is paralyzed, fails to respond to the scan tool, doesn't do it's job, is go to the dealership (or a junkyard), or borrow a "known good" unit out of another vehicle, and plug it into a problem vehicle. Modules today are often $500 and up...
As I said above, this is an absolutely fantastic way to FRY a second module, and if it's a "known good" loaner, thereby disabling a SECOND vehicle.
Techs who simply don't have extensive electronic backgrounds are EXPECTED, and REIMBURSED BY WARRANTY to follow the factory supplied diagnostic tree.
That doesn't mean the tree is correct. Or complete.
Nor does a tech have to be a real electronics GURU to check ECM inputs/outputs for reasonableness. Anyone who can use a meter properly can measure voltages, resistances, current, and check continuity. They just know it NEEDS TO BE DONE before calling a module, ANY module "bad" or stuffing a brand new one in, especially when it costs hundreds of dollars.
It goes a LOT faster when you have a helper who can read a schematic so one guy can probe inputs/outputs CALLED OUT by the guy reading the schematic. Counting pins and getting onto the right line is always a challenge with todays miniature connectors/pins.
Complicating Warren's repair is that his tuner is electronically "keyed" to his ECM, so ECM replacement is even more complex, and a SECOND FAILURE will add even more grief to the repair. (And weeks of delay as the tuner is sent back to the factory AGAIN to be re-keyed)
When I say "module" it doesn't have to be an "engine ccontrol module" it could be something as simple as an ignition "module." Basically ANY 'black box" with transistors inside, that has inputs, outputs, and 12V and ground power inputs. When a module, ANY module fails, the cause is USUALLY OUTSIDE of the module itself.
I'll report back in a few weeks on whether Warren's ECM truly did die "of old age." (rare) and its replacement was correct, or if now he's looking at SECOND module replacement.
Hopefully this little treatise will save those of you doing your OWN diagnosis and repairs from getting to buy TWO instead of one replacement modules, as they tend to be the most expensive parts on a bike/car anymore.
Questions?
