MIL light is on, bad battery in ECU Ram chip
Discussion
My MIL light recently came on. It was an intermittent thing, but when it got persistent, I checked the ECU log and a battery fault was recorded. The battery mentioned is the one in the ECU Ram chip. I bought a new chip on eBay 2 years ago. The date code on the chip was 2006, already an 9 year old battery ! But it was newer than the one in my Cerb, so I replaced it.
My newer chip (battery) is bad now but why ? As far I know, these chips are not anymore manufactured and most likely l got a chip from an old stock with a new label printed. So watch out for refurbished chips !
My newer chip (battery) is bad now but why ? As far I know, these chips are not anymore manufactured and most likely l got a chip from an old stock with a new label printed. So watch out for refurbished chips !
Luckyone said:
How do you know the fault was for the ECU Ram chip?
I replaced my "new" chip with the original one and the MIL light was gone. To make sure this was the problem I put the new chip in and the fault was back.Luckyone said:
There is only one entry for that in the help file: BAT FLT
This fault is shown if the battery voltage falls below 11 V, or rises above 17v whilst engine peed is above 1500 RPM.
Battery fault can be caused by:
1. Faulty alternator causing over or under charging.
2. Faulty battery .
3. Poor earths from ECU to battery
4. Poor power feed to ECU from battery.
that is from the help file for the speed six, so I assume the BAT FLT is Battery Voltage Log Fault.
You are right, I downloaded the data-sheet of the chip and I can't see a way how the voltage of the chip battery can be measured by the ECU. However, the software could disconnect the power of the chip and check if it holds the data. But this seems very unlikely. This fault is shown if the battery voltage falls below 11 V, or rises above 17v whilst engine peed is above 1500 RPM.
Battery fault can be caused by:
1. Faulty alternator causing over or under charging.
2. Faulty battery .
3. Poor earths from ECU to battery
4. Poor power feed to ECU from battery.
that is from the help file for the speed six, so I assume the BAT FLT is Battery Voltage Log Fault.
Luckyone said:
I keep getting Battery Voltage logged as a fault which seems odd as it never meets the above conditions, it does drop to low 11s when the revs drop very low after resetting the adaptive, but that is well below 1500 RPM.
So if it's really the ECU battery it's taking about it could explain a lot! It seems odd though as in the MBE software it shows the current state of all the sensors & under them on the same page is the logged faults, there is only one for battery & the log fault corresponds to the window above that shows the current car battery voltage.
There must be other conditions to turn the MIL on, if I push the red button the MIL comes on and goes away as soon the engine fires. In my case the MIL never came on during driving, but immediately after starting. My 12V main battery is only a year old, and the engine starts on first try even after weeks of no use. So if it's really the ECU battery it's taking about it could explain a lot! It seems odd though as in the MBE software it shows the current state of all the sensors & under them on the same page is the logged faults, there is only one for battery & the log fault corresponds to the window above that shows the current car battery voltage.
Peter
The battery can not be replaced on these chips, but there are alternative solutions as the example above. I bought mine on eBay, they were about 8£/each. The newer MBE ECU uses a separate (replaceable) battery. These chips have a built in "seal", the battery is internally not connected when new. The first time power is applied, the battery is connected to the circuit (for ever).
According help file a logged error will turn on the MIL until its reset by the Pc software. And where is the log ? Yeah, in the RAM Chip with the battery. With my new chip I had reset the fault several times during this week and since the old one is back in no problems at all.
An other thing crossed my mind, the original chip had 4.75 volts as a minimum operating voltage, the new chip operates down 4.5 volts. Could this cause some uncontrolled writes by the CPU when the main battery voltage drops during starting ? In the ECU this certainly regulated from 13.8 to the 5volts used internally. I'll never know
According help file a logged error will turn on the MIL until its reset by the Pc software. And where is the log ? Yeah, in the RAM Chip with the battery. With my new chip I had reset the fault several times during this week and since the old one is back in no problems at all.
An other thing crossed my mind, the original chip had 4.75 volts as a minimum operating voltage, the new chip operates down 4.5 volts. Could this cause some uncontrolled writes by the CPU when the main battery voltage drops during starting ? In the ECU this certainly regulated from 13.8 to the 5volts used internally. I'll never know
gruffalo said:
Peter, have you measured the main car battery voltage with the car running at a few 000 RPM.
No, as the MIL never came on during driving.gruffalo said:
THe MIL light comes on at over 17 volts and the alternator voltage regulators in the alternator often fain in a state that lets the alternator reach in excess of 17 volts.
If this is the fault then your car will start but your battery won't last long due to being overcharged.
Correct voltage across the battery terminals with the engine running at a decent speed should be around 13.8 volts.
The regulators often fail along with an old battery due to a defective battery putting excessive load on the regulator.
Regulators normally fail gradually with the MIL light coming on occasionally but then getting progressively worse, a common indicator of a failing regulator is a pulsing of the internal lights and instrument lights.
Good to know, I will monitor things with the old chip back in now.If this is the fault then your car will start but your battery won't last long due to being overcharged.
Correct voltage across the battery terminals with the engine running at a decent speed should be around 13.8 volts.
The regulators often fail along with an old battery due to a defective battery putting excessive load on the regulator.
Regulators normally fail gradually with the MIL light coming on occasionally but then getting progressively worse, a common indicator of a failing regulator is a pulsing of the internal lights and instrument lights.
Thanks
Peter
Gentlemen, it was certainly not my intention to cause confusion with my original topic/message. What I'm trying to say is, if you observe logged battery faults it could be the ram chip. It was the case in my car. When the problem happens, the MIL and the beeper is permanently on (very annoying if you have a half hour drive home).
When I reset/cleared the logged fault (via the PC software), the MIL and beeper went off too. I had to do this on about 5 occasions and it always came on when I started the car, never during driving. So I replaced the chip with my original one and since that chip is in, the problem has gone too. Nothing else was changed.
Of course the chip holds the adaptives and log when you remove it, and later put it back in its socket, or even if you put it into an other car. But this doesn't matter because I had reset the log fault several times on the bad chip.
If you order a chip, try to get the DS1230AB (which is the original type) and not the DS1230Y. My "bad" one was a DS1230Y, this type protects the RAM if voltage drops below 4.25 Volts and operates from 4.5 - 5.5 Volts (ECU internal supply voltage derived from 13.8V main battery). The limit for the DS1230AB is 4.5 Volts and 4.75 - 5.25 Volts.
Thanks for all input. Peter
When I reset/cleared the logged fault (via the PC software), the MIL and beeper went off too. I had to do this on about 5 occasions and it always came on when I started the car, never during driving. So I replaced the chip with my original one and since that chip is in, the problem has gone too. Nothing else was changed.
Of course the chip holds the adaptives and log when you remove it, and later put it back in its socket, or even if you put it into an other car. But this doesn't matter because I had reset the log fault several times on the bad chip.
If you order a chip, try to get the DS1230AB (which is the original type) and not the DS1230Y. My "bad" one was a DS1230Y, this type protects the RAM if voltage drops below 4.25 Volts and operates from 4.5 - 5.5 Volts (ECU internal supply voltage derived from 13.8V main battery). The limit for the DS1230AB is 4.5 Volts and 4.75 - 5.25 Volts.
Thanks for all input. Peter
Noblebenn said:
...
Fast forward a year and it happened again. Started to happen every 1 in 10 starts until it became 1 in 5.
It would seems that something is causing the chip to deteriorate slowly and when the car doesn't fire up first time the adaptive maps are lost.
....
It's hard to believe the chip is deteriorating. Inside the "chip" is only memory, a battery and some logic to switch between battery or external supply. In other words, the only thing that can deteriorate is the battery. Fast forward a year and it happened again. Started to happen every 1 in 10 starts until it became 1 in 5.
It would seems that something is causing the chip to deteriorate slowly and when the car doesn't fire up first time the adaptive maps are lost.
....
When it happens, are you able to start and drive away or do you need to reset the maps to keep the engine running ?
The logic inside the ECU is designed in way that the CPU is not able to mess up the maps during cranking (or during any other voltage drops from the main battery).
What you maybe could do is: When you get home after a ride, don't turn the engine off and readout the maps. Do this maybe 3 times until the value in each cell doesn't change anymore, or at least not significantly. Wait until the problem appears, then compare this map with your previous ones. If they are nearly the same (especially around idle) we are looking at the wrong thing. If they are way apart the question is, what would force the ECU to correct these values to such an extent ?
Maybe that helps ?
BTW. After I put my original chip back in, the engine runs faultless since then.
Peter
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