2001 V70 2.4T ECM-8410 5-volt power supply signal too low

[prwood]

I just recently started seeing an "ENGINE SYSTEM SERVICE REQUIRED" message on my DIM. There aren't too many accompanying systems - an occasional hesitation when starting up from a stop, and an occasional misfire (I also have an intermittent code for signal missing to ignition coil #3 which I assume is what's causing the misfire). I broke out VIDA/DiCE to get some more info. I found the following error, "ECM-8410 5-volt power supply signal too low". The diagnostic workflow says to check the voltage between the ECU and various components:

- MAF sensor
- Boost pressure sensor
- A/C pressure sensor
- Fuel tank pressure sensor

I am familiar with the location of the MAF and Boost pressure sensors, but I'm not sure where to find the A/C pressure sensor.

Also, for the fuel tank pressure sensor: I know some models have a fuel pressure sensor mounted on the end of the fuel rail on the manifold, but mine does not have that - so is this talking about the sensor mounted in the fuel tank itself? If so, would that mean pulling off the rear seats to get access to the pigtail for that sensor?

My thought is to try and find all of these connectors and visually verify that there aren't any breaks in the cable, before pulling the ECU to trace the signal cable with the multimeter.

Also, VIDA recommended reading off the voltage for the 5V power supply through the software, which I did, and it read out as 0.87V. VIDA says anything below 4V is considered low, and 6V is considered high. I had seen a reference in another forum thread that this could potentially be a result of overall low system voltage, rather than an issue in the 5V power supply, and that one should verify that system voltage is ~14V while the engine is running. VIDA reported that my voltage was 12.1V, so I'm wondering if there could be a problem elsewhere in the charging system.

I'd appreciate any thoughts on the above. Thanks!

[jonesg]

VIDA seems to do funny things with voltage, like run it down very quickly.
I put a volt meter on the battery terminals, engine idling should show 14v + .

If not, check the small signal wire (spade plug) on the back of the alternator. Mine was corroded.
Next suspect is the regulator.
Ground wires on the driver fender can be cleaned.

With good supply voltage , maybe the ECM needs reseating/cleaning.

[prwood]

Ok, so I did some digging yesterday. Here's what I found:

- Voltage measured across battery terminals while engine running: 13.87 volts <-- is this too low?
- Voltage measured across battery terminals when car off: 12.0 volts
- Voltage measured across battery terminals when battery disconnected: 12.27 volts

I also pulled the ECU, and checked the connection between the following as described in VIDA:
- ECU Terminal A39 and MAF connector terminal 4
- ECU Terminal A39 and boost pressure sensor terminal 4
- ECU Terminal A39 and A/C pressure sensor terminal 3 (this one is a PITA to access)

Resistance looked good on all of them. I visually inspected the cables and connectors as well and they all looked good, no sign of breaks.

VIDA also said to check the cable between the ECU and the fuel tank pressure sensor, but I'm not really up for pulling the seats off at this point to do that.

I reconnected everything, also QD electrical connector cleaner and then air blasted the ECU terminals, then reseated the ECU. I haven't driven it around too much since then, but I'll keep an eye on it and see if the error comes back.

[jonesg]

Yes thats a bit low at the battery terminals,

If the output is the same 13v at the alt then the odds are on the regulator, $45.