ABS Alarm

PlasticMac said:
I'd suggest finding a good auto electrician, and asking if they can check your alternator and battery, and go from there.
Try Googling "auto electrician near me"
Yes, keep the faith indeed!
Mac.
Click to expand...
Just as an added comment, if the alternator, especially the diode pack, is faulty, then as well as the obvious low voltage, (a good battery and alternator would shows around 13.5 Volts), the voltage could be spiky, electrically noisy, not nice smooth DC. That electrical "noise" would upset the electronics, and cause systems, such as ABS to malfunction.
You must sort the power supply out, before looking elsewhere.
Mac.
 
Howey said:
By seemed OK was the resistance within range?
Click to expand...
The low voltage in the log would have been the voltage at the ECU, so although the engine earth is a very important link in the power distribution, it's not the cause of the logged problem.
Without making voltage and current measurements on the car, impossible to differentiate between battery and alternator. And of course, if either is faulty, especially the alternator, the other will suffer too.
Mac.
 
PlasticMac said:
The low voltage in the log would have been the voltage at the ECU, so although the engine earth is a very important link in the power distribution, it's not the cause of the logged problem.
Without making voltage and current measurements on the car, impossible to differentiate between battery and alternator. And of course, if either is faulty, especially the alternator, the other will suffer too.
Mac.
Click to expand...
If the earth is compromised the complete charging system is compromised. Start with the basics and rule them out first. An additional earth is a few pounds and every A2 should have one
 
Howey said:
If the earth is compromised the complete charging system is compromised. Start with the basics and rule them out first. An additional earth is a few pounds and every A2 should have one
Click to expand...
Your right, and I was about to post an apology, and a recant.
The engine earth is the alternator earth, so definitely a potential,and likely, cause of the symptoms.
Mac.
 
Howey said:
By seemed OK was the resistance within range?
Click to expand...
i think so Howey! Perhaps I'm not doing it right though
My test was altenator case to chassis
there was not that much of a Volt drop. 0.1V i think
I did not test the B post to battery +ve as the battery is too far away and i'm without a suitable wire length at the moment

Interestingly I ran the VDCS-lite again with the car running on the drive in neutral
I've attached the logs
The logs showed Voltage Supply varying as i put electrical load on ... (heater/heated seats/ full beam etc)
Down to 11.6V at times.

As I turned electrical loads off the voltage supply came back up
The voltage measured with a mutimeter at the battery was steady throughout as far as i could tell. Even when VDCS was giving a voltage supply of less than 12V the battery itself was reading 14+V. I'm not sure where the Voltage Supply is measured from ... the altenator ot the coil pack??
Not sure if thats unusual re the variance

All was well in terms of the alarms...so I decided to try some revs (from data row 291) - the supply volts came up to 13.1 and then the alarm came on (row 302 - highlighted in yellow) at which point i marked the logs as quick as possible - Mark 6.

I cant see anything obvious from the logs....

So I was hoping to see the alarm come on on the voltage supply drop
The plot thickens!

Any thoughts more welcomed

All the best
 

Attachments

smilesbernard said:
i think so Howey! Perhaps I'm not doing it right though
My test was altenator case to chassis
there was not that much of a Volt drop. 0.1V i think
I did not test the B post to battery +ve as the battery is too far away and i'm without a suitable wire length at the moment

Interestingly I ran the VDCS-lite again with the car running on the drive in neutral
I've attached the logs
The logs showed Voltage Supply varying as i put electrical load on ... (heater/heated seats/ full beam etc)
Down to 11.6V at times.

As I turned electrical loads off the voltage supply came back up
The voltage measured with a mutimeter at the battery was steady throughout as far as i could tell. Even when VDCS was giving a voltage supply of less than 12V the battery itself was reading 14+V. I'm not sure where the Voltage Supply is measured from ... the altenator ot the coil pack??
Not sure if thats unusual re the variance

All was well in terms of the alarms...so I decided to try some revs (from data row 291) - the supply volts came up to 13.1 and then the alarm came on (row 302 - highlighted in yellow) at which point i marked the logs as quick as possible - Mark 6.

I cant see anything obvious from the logs....

So I was hoping to see the alarm come on on the voltage supply drop
The plot thickens!

Any thoughts more welcomed

All the best
Click to expand...
The voltage in the ECU diags is the voltage at the ECU itself, under the floor, uses the chassis earth, at the battery, but not the engine earth. If the engine earth is bad, then the power out of the alternator, when the engine runs, if affected. Any resistance will result in voltage drop, and as the power into the battery after a start is very high, so would be that voltage drop.
If you start the log, with the ignition on, but the engine not running, the log will show us the voltage at the ECU, without any influence from the engine earth. We'll also see how the voltage behaves when the starter load is drawn, and how the alternator does trying to replace the energy taken by the starter.
With a healthy battery and alternator, you will see 13.5 - 13.8 Volts with the engine running, and at one point in the new log I do see 14.1 Volts! Downhill from there though.
The voltage at the ECU, with the ignition on, but the engine not running is purely the battery voltage. Applying a bit of load, dipped beam would be good, again, before starting, the log will show the battery copes with that load, and, probably give us a good clue about the battery's condition. Turn the lights Off, then start the engine, and once it's running switch the lights on again. With the engine running, the engine earth comes into play, so again, possible clues.
Mac.
 
Last edited:
thank you all for the help with this
I followed that advice @PlasticMac
this is with the older battery as i needed to retrn the battery I was using yesterday to my wifes car!
It was fully charges recently .
this log shows a good progression
marker 0 - ignition on. no electrical load. engine off
1- lights on
2. lights off
3. engine started
4. lights on
5. then full beam
6 then heater full temp and fan
7. both heated seats on full
8. seats off
9. cant remember!
10. checked battery volts durectly with multi meter and was reading 12.8V vs.. <12v on the ECU/log
@540 secs started to rev the engine
Quickly the alarm came on.

When i checked the error codes...... it was saying the usual manifold air pressure thing:

17961 - Barometric / Manifold Pressure Signals: Implausible Correlation
P1553 - 35-10 - - - Intermittent


So it seems to be linked to reving... or its just coincidence that both times when running on the driveway it alarmed as soon as i moved to high idle revs
When driving this seems to be after about 3-4 mins ... so i cant tell if its time based or rev based.
I should / could just leave it with no revs for 15 mins on the drive in low idle then rev.... as a test i guess

Many thanks for your thoughts

ALl the best
 

Attachments

I'll look at the log tomorrow.
I'd not worry about anything, other than the supply voltage.
The spec for controller, including ECU, supply voltage is 12.0...15.0 V, (from the label file, and common across all controllers).
So, the controller functionality is unlikely to be reliable at 11.2.
That, for me, means reading such as manifold pressure, and ABS warnings, are not reliable diagnostics, other than as an indication of the problem, until the reason for the low supply voltage is found, and fixed.
If the battery voltage, at the battery, is 12.8, but very much lower at the controller, then poor connections between the battery, and the car's power distributions point, in the under floor compartment, are the first suspects. Both positive and negative/earth.
The possible correlations between rpm and symptoms could well be the effect of vibration on the dodgy contact.
Mac.
 
It's early, so it might be me, but although you started the engine at marker 3, the engine speed shows the engine running from the start of the log ...
Mac.
Screenshot 2025-02-03 08.16.42.png
 
hmmm
Just looking at the log file again ...
It is early but mine only has engine revs from marker 3 @ 27secs in
reattached just in case
Thanks for info re the ECU voltage as likely source
So wondering how to test that ....and trace any voltage drops
Interestingly when the Voltage supply log reading was high ... over 13V. Battery was 12.8... also when log was low this was around 12.8V
So battery only getting a tricle charge at best
I'm unsure of the cable runs and where to hunt for voltage drops or high resistance
SOunds like from what you say the +/-ve cabling would run from battery to ECU.

I've been under the passenger floor before to have a nose about but that is all really
I did remove headlight and checked / cleaned reseated the chassis ground a few weeks ago
I guess a long cable run from bat +ve to allow voltage drop testing on the alternater +ve side would be interesting too

I would take it to an auto elec but to be honest i've done nothing but spend out one thing after another since i recovered the car unloved from mother in law. Its reached the point of vanishing economic viability :) Decided if i cant fix it myself it will have to go . Like it though so fingers crossed

thanks for all the help
 

Attachments

smilesbernard said:
hmmm
Just looking at the log file again ...
It is early but mine only has engine revs from marker 3 @ 27secs in
reattached just in case
Thanks for info re the ECU voltage as likely source
So wondering how to test that ....and trace any voltage drops
Interestingly when the Voltage supply log reading was high ... over 13V. Battery was 12.8... also when log was low this was around 12.8V
So battery only getting a tricle charge at best
I'm unsure of the cable runs and where to hunt for voltage drops or high resistance
SOunds like from what you say the +/-ve cabling would run from battery to ECU.

I've been under the passenger floor before to have a nose about but that is all really
I did remove headlight and checked / cleaned reseated the chassis ground a few weeks ago
I guess a long cable run from bat +ve to allow voltage drop testing on the alternater +ve side would be interesting too

I would take it to an auto elec but to be honest i've done nothing but spend out one thing after another since i recovered the car unloved from mother in law. Its reached the point of vanishing economic viability :) Decided if i cant fix it myself it will have to go . Like it though so fingers crossed

thanks for all the help
Click to expand...
That's fine, thanks.
This second log was with a different battery than the first, correct?
The voltage in this one looks good, the expected dip at cranking, quick recovery, fine.
The manifold pressures look fine too.
(Throttle blip at the end of the log).
It seems like changing the battery changed something else. From log comparison, the first battery is suspect, (but, in fact, known good), whereas the second battery/alternator combo look very good.
Hints at connection to the battery or battery earth. Check the strip fuse on the + battery terminal is tight too.
Mac.

RPM_100 and Voltage.png
 
PlasticMac said:
That's fine, thanks.
This second log was with a different battery than the first, correct?
The voltage in this one looks good, the expected dip at cranking, quick recovery, fine.
The manifold pressures look fine too.
(Throttle blip at the end of the log).
It seems like changing the battery changed something else. From log comparison, the first battery is suspect, (but, in fact, known good), whereas the second battery/alternator combo look very good.
Hints at connection to the battery or battery earth. Check the strip fuse on the + battery terminal is tight too.
Mac.

View attachment 134349
Click to expand...
Here's the first log for comparison:
Mac.

RPM_100 and Volts.png
 
thanks so much for this
Ok so i'll have a look at all the connections
I wonder how to work along from battery to main points to test as i moove fwd
Do you know of any wiring schematics at all?
Thanks again
 
smilesbernard said:
thanks so much for this
Ok so i'll have a look at all the connections
I wonder how to work along from battery to main points to test as i moove fwd
Do you know of any wiring schematics at all?
Thanks again
Click to expand...
I'd start in the area around the battery, as changing your battery transformed the voltage at your ECU.
The battery that gave poor voltage, was a known good one, so, probably not the battery itself.
That hints at a connection that the act of physically changing the battery, disturbed.
So, start there.
Battery posts, and clamps, strip fuse, earth point, for starters.
Mac.
 
Thanks Mac
And the earth point - that's under the nearside front headlamp as chassis attachment ? I've looked at that and cleaned but wondering if there is another to check or where the other end/s of that are
Thank you
 
smilesbernard said:
Thanks Mac
And the earth point - that's under the nearside front headlamp as chassis attachment ? I've looked at that and cleaned but wondering if there is another to check or where the other end/s of that are
Thank you
Click to expand...
I would concentrate on the battery compartment, as the actual, mechanical changing of the battery, (not electrical), seems to have made a big difference. So connections that were moved, on purpose, or just as a consequence, during the change.
The battery clamps, wire to battery post, the strip fuse, with two small nuts, on the + side of the battery. The state of the wire to clamp joints, + and -.
I'm not sure where the cable from negative side of the battery is bolted to the chassis, but needs checking, if someone can tell us where it is. The circuit diagram says it's on the chassis leg, between the B and C pillars, so underneath somewhere.
Sorry to be a bit vague.
Mac.
 
PlasticMac said:
I'm not sure where the cable from negative side of the battery is bolted to the chassis, but needs checking, if someone can tell us where it is. The circuit diagram says it's on the chassis leg, between the B and C pillars, so underneath somewhere.
Click to expand...
Good Evening Mac,

All I know.

P

Thread 'Main battery earthing point'

Where does the main battery earth cable attach to the car, has anyone earthed the battery directly to the bodywork at the rear of the car and if so where did they attach to?

Probably 6 here.

1738782698252.png


Andy
 
PlasticMac said:
I would concentrate on the battery compartment, as the actual, mechanical changing of the battery, (not electrical), seems to have made a big difference. So connections that were moved, on purpose, or just as a consequence, during the change.
The battery clamps, wire to battery post, the strip fuse, with two small nuts, on the + side of the battery. The state of the wire to clamp joints, + and -.
I'm not sure where the cable from negative side of the battery is bolted to the chassis, but needs checking, if someone can tell us where it is. The circuit diagram says it's on the chassis leg, between the B and C pillars, so underneath somewhere.
Sorry to be a bit vague.
Mac.
Click to expand...
Thanks Mac very helpful
I'll have a hunt and report back
Strangely this all started with the battery that is back in again. I only removed it and swapped with another to see if the battery was at fault!
And the alarm is still triggering
But I'll check and see if I can stop the goltsgr dropping at the sense point on the ecu that vdcs sees
Thanks again
 
Andrew said:
Good Evening Mac,

All I know.

P

Thread 'Main battery earthing point'

Where does the main battery earth cable attach to the car, has anyone earthed the battery directly to the bodywork at the rear of the car and if so where did they attach to?

Probably 6 here.

View attachment 134426

Andy
Click to expand...
Thanks Andy that's a great help
So likely jack up and search under the car ? Or do you know if this is internal and needs interior stripping out to access?
Thanks again
 
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