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2005 Mk2 With Battery Charge Light On.


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My 2005 focus 1.6 has a problem or 3. Firstly I had 2 alarms coming up regular about the ABS I eventually cure one by changing the rear left wheel hub/bearing assembly. the front right one I change the sensor which was easy but its still reporting a fault so its booked in for the Hub/bearing assembly to be replaced. I Hope that will be the end of that. I also have an alarm about the battery smart charge system. now I have checked the battery is correct( a calcium one) I have looked for broken or chafed wires but found nothing wrong. The voltage at pin 3 of the connector is virtually the same as the battery voltage. The battery is difinately being charged. shows 14.3V when engine running but does drop back a little ( 13.8V ish) after a while. I scoped the other pins and I have attached the file to this posting. Does anyone know if the trace I got is correct, and if it is what do I do next.

Other points I diconnected the alternator plug while the engine was running and the revs increased quite dramatically. Also if I clear the DTC codes the smart charge one comes back even without the engine running.

Any help or advice offered would be greatly apprieciated.post-38380-0-15805200-1429019247_thumb.p

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Check the resistance of the three wires from the fusebox to the alternator and ecu to alternator first...obviously a reading of more than 1 is bad.

I would then look at the battery when the ignition is off.

Then it would be the alternator to check output when idling...but as you mentioned that may be ok.

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Pin 1 =

Pin 2 =
Load Request

3 = Reference Voltage

Now, pin3, must MATCH battery voltage ! Its fed from a fuse in the CJB,
and a high resistance on the fuse contacts causes a volt drop, and the smart
charge drops out !

Next pin 1 & 2 need checking back to the PCM for resistance, isolation from
ground and each other. If ok, its out with the scope.

Pin 2 is the request from the PCM to the
This will be a square wave pattern that will change with load request. So
lights, screens etc on and monitor for a change in the pattern. (Obviously back
probing with the plug connected)

change in the pattern means no request from the PCM, you should now suspect a
PCM fault. Correct pattern and move on.

Pin 1 is the feedback from the
and MUST remain a constant square wave pattern. If this pattern mirrors the one
on pin 2, the smart charge part of the
alternator is faulty, and a new
unit is required.

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Thanks for showing an interest in my problem. However all that has been written so far I already knew from previous downloads etc.

2 points to make:- 1 switching on additional loads does not increase the output request from the PCM. the reason being is that the smart charge system is designed to increase the charging of a calcium battery when the enviroment under the bonnet is cold. it does it apparently by using the external temperature sensor and the engine temperature. if they are cold then a calcium battery can take a much higher charging rate. This is explained by someone else on this forum somewhere who is an auto electrician. Point 2. I have done a physical check of the wires from the alternator connector and not found anything wrong also I did an oscillascope trace at the alternator connector, the results are on my original posting. It is not possible to do a resistance check of the wires from the alternator to the PCM as the connector at the PCM cannot be removed. It is held in place with a shear bolt and will require drilling out. I also measured the voltage on the battery terminal and at the alternator. as they were virtually the same (within 10 millivolts). There cannot be much resistance in the line.

Is there anybody that knows what the waveforms actually look like on a good System.

Any more ideas please.

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That's all from a ford specialist auto electrician so what it says is true its the same method dealers use switching on loads does increase the request from the pcm if its 14.4v with all off and you switch on say the rear screen it drops then will increase back to 14.3 14.4v its also not exactly how smart charge works yes a cold battery takes a higher charge but iys dependant on the temp of the electrolyte and as that increases the battery charge voltage drops to compensate you will get a fault if the battery is passed its best load testing the battery is the first step if you haven't already done this

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Here is the latest on my problem. and that is, I do not have a problem anymore the car is fixed.

Rear left ABS sensing cured when I changed the bearing and sensor combined.

Front right ABS sensing was not cured when I replaced the sensor so I had a garage replace the front bearing etc. this did not cure the problem so I swapped the sensors over left to right etc. and guess what. the fault moved aswell. so the sensor that I bought cheaply on eBay was in fact broken even though it was new. silly me. Sourced a new sensor (£27) fitted it then all ok.

Now to the battery light problem. I always get the DTC for the Smart charging circuit being faulty. However when I replaced the LED on the instrument cluster circuit board the light was not on anymore. I had not removed the LED's by the way, It was the previous owner. He had also removed the led for the ABS and ESP. Anyway having replaced them, all is now well, though The smart charge code is still re-occuring I may look again into that.

Thanks for the advice and interest shown. :D

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