Hello again,
just as I got the Punto (1998 75 SX) running smooth and nice after that annoying jerking (lambda sensor was a bit too slow to react) and rev limit (new rpm sensor), I encountered a new electrical problem.
The ECU stays powered after I turn the key off.
Now the ECU staying on for a few seconds after key off is normal, as it monitors coolant temperature and switches the radiator fan (air conditioned model). But this time it's not a few seconds, it's on indefinitely. This doesn't happen every time I switch the car off and I haven't noticed any pattern to it, just that it's getting more and more frequent.
The engine must have been running, even for a second, for the power to stay on. I can test it being on by measuring sensor voltage feeds or using a diagnostic tool. Also doesn't need the coded key to start it, as it thinks the engine just has just been stalled by the driver for a few days.
This causes issues; battery drain (few hundred milliamperes to the ecu and sensors), and very bad starting due to a P0115 coolant temperature sensor error. The sensor is fine, so is the wiring. Maybe the computer doesn't believe the coolant signal after being on for several hours. By removing the fuse to the ECU main battery supply, it switches off and doesn't come on again when the fuse is reinstalled. By doing this it works nicely, no errors and no drain. But it isn't fun to do every time I park, and I maybe lose the stored self-learning values?
It did this once in the winter, then a few times in spring, now when the weather is hot, it's daily.
Removal of ignition lock connector, IGN fuse, main relay, rpm sensor, AC computer, AC pressure switch or coolant temperature sensor doesn't switch it off.
Sorry for the long post, but I have been scratching my head for weeks with this thing and can't figure it out on my own. Any guesses from you guys?
just as I got the Punto (1998 75 SX) running smooth and nice after that annoying jerking (lambda sensor was a bit too slow to react) and rev limit (new rpm sensor), I encountered a new electrical problem.
The ECU stays powered after I turn the key off.
Now the ECU staying on for a few seconds after key off is normal, as it monitors coolant temperature and switches the radiator fan (air conditioned model). But this time it's not a few seconds, it's on indefinitely. This doesn't happen every time I switch the car off and I haven't noticed any pattern to it, just that it's getting more and more frequent.
The engine must have been running, even for a second, for the power to stay on. I can test it being on by measuring sensor voltage feeds or using a diagnostic tool. Also doesn't need the coded key to start it, as it thinks the engine just has just been stalled by the driver for a few days.
This causes issues; battery drain (few hundred milliamperes to the ecu and sensors), and very bad starting due to a P0115 coolant temperature sensor error. The sensor is fine, so is the wiring. Maybe the computer doesn't believe the coolant signal after being on for several hours. By removing the fuse to the ECU main battery supply, it switches off and doesn't come on again when the fuse is reinstalled. By doing this it works nicely, no errors and no drain. But it isn't fun to do every time I park, and I maybe lose the stored self-learning values?
It did this once in the winter, then a few times in spring, now when the weather is hot, it's daily.
Removal of ignition lock connector, IGN fuse, main relay, rpm sensor, AC computer, AC pressure switch or coolant temperature sensor doesn't switch it off.
Sorry for the long post, but I have been scratching my head for weeks with this thing and can't figure it out on my own. Any guesses from you guys?
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