ABS/ESP pre-charge-pump low voltage

[radekb]

Hi! At the beginning I want to apologize for my english
Greetingz from Poland

I've got problems with ABS/ESP. PP2000 show problem with low-voltage of pre-charge pump.
Look at the wiring diagram:


I did these things:

I performed actuator tests in PP2000 (ABS/ESP) - every component works fine - both the ABS pump and the ESP preliminary pump. And now, a total mystery - to the controller on the ABS pump (7806) pin 10 is reaching 9,85V from the relay, and pin 14 is reaching 13,6V. I think that it should be about 14.1V - am I right? To the ESP pump (pre-charge-pump) connector 11.4V voltage is reaching (on the unplugged pump), but when I plug it on PP2000 shows a low voltage: 3.9V. According to PP2000, the correct voltage should be 10-16V. I've improved all the earths and the earth on pin 13 on the ABS pump (7806) is perfect, whereas the earth at the connector for the pre-charge-pump has high value (15 kOhm). Help, because now I don't understand what the hell is going on To relay 7802, voltages are reaching perfectly 14.2V. Both relays are replaced to another one (.

[steve_earwig]

Hello from Croatia Your English is fine, don't worry.

I'm afraid I lost my access to SEDRA (the wiring diagrams) with Windows 7, I've never had the patience to get it going on Windows 10 (the older I get, the less patience I have but the more hammers I buy...) and I see that all my useful Internet links don't go anywhere now so the best I can do is give a few thoughts:

And now, a total mystery - to the controller on the ABS pump (7806) pin 10 is reaching 9,85V from the relay, and pin 14 is reaching 13,6V. I think that it should be about 14.1V - am I right?

They should be battery voltage. I mean, if the pictures of relays can be trusted (don't assume any of these diagrams are the truth!) then both should be fed straight from the main fuses and have battery voltage on them. Is the 9.85v saying there's a bad connection somewhere? Does it carry any current? This is where a meter can be misleading, a test lamp would be better. Or even just a bulb.

To the ESP pump (pre-charge-pump) connector 11.4V voltage is reaching (on the unplugged pump), but when I plug it on PP2000 shows a low voltage: 3.9V.

I'm not sure which is the precharge pump (ffs I can't even look that up any more ) but again there is low voltage, maybe this can't carry much current either and the 3.9v is what it drops to when there is a load on it.

I've improved all the earths and the earth on pin 13 on the ABS pump (7806) is perfect, whereas the earth at the connector for the pre-charge-pump has high value (15 kOhm).

I'm only seeing 1 earth on the diagram (M80 > M7806 > pin 13), maybe the pre-charge pump isn't even on there (?) Basically if it doesn't start with an M it's not a real chassis ground and what you are seeing is possibly the output stage of something.

Meh, that's probably not a lot of help but hopefully it'll give you a few ideas.

Good luck!

[radekb]

Thanks for Your advices!
Hammer - yes, this is really useful thing Magical
Well - I found one more clue I did actuator test one more time - I've noticed that relay connected to abs the pump "clicked" but abs pump was dead. I hit pump slightly (yes - hammer is made by gods ) and it starts to work. Another actuator test was done without problem - low voltage error for pre-charge-pump still exists. I've bought another one abs pump and I will try to replace it. I hope it will resolve this problem.
The second clue is voltage on relay connected to abs pump. According to wiring diagram relay's output should be 0 or battery voltage but it has 4,8V in steady (instead of 0V) and battery voltage (14,1 V) when it's activated....

I think that pre-charge-pump means esp pump, hidden below brake servo, behind the battery.