Hello everyone, just been out in my car but had to limp home, won't have access to a fault reader til later, in the meantime anyone want to hazard a guess? Had the injector seals replaced about 18 months ago.

P0643 Sensor Reference Voltage A Circuit High

 

Been told this could be due to my egr valve needing cleaning?

Could be the case, the carbon builds up and the valve then sticks open, causing the light and limp mode.  Pretty common in most diesel cars nowadays.

Can I clean it without removing it? I don't want to remove the fuel filter if I can incase it doesn't start.

Is the fuel filter in the way? Because you will need to take it out. You don't want to run the risk of the clumps circulating, plus its easier to make sure the job is done right. Be carful removing the plug to the valve, you don't wanna break it and cause more issues.

 

Yeah fuel filter needs to be removed but I'm worried I won't get the car to start once I put it back in.

Took the diesel filter & egr valve out, cleaned it, will refit after shopping lol, has anyone blanked the egr valve off?

Can't for the life of me get the clip that holds the egr to the manifold back on.

Got the EGR clip back on, used a syphon to pull the fuel through the filter & now it's running again. No EML & no sluggish accelerating.

My car is now juddering on low revs, I thought at first it may be an air lock but I've done 150 miles since cleaning the EGR & it's still happening.  Any ideas?

On 10/26/2018 at 11:45 AM, BP2411 said:

P0643 Sensor Reference Voltage A Circuit High

If this code is correct, it will be nothing whatever to do with the mechanical operation of the EGR valve, ie solved by cleaning.

There are quite a few sensors on all modern cars, EGR valve position, Turbo valve/wastegate position, MAF, MAP, Fuel rail pressure, most temperature sensors, are a few, and these need a reference voltage, usually 5v, to work. These 5v references are generated inside the ECU, it seems like there are only a one or two generated references that are used by several sensors. Makes sense to me, to keep cost & component count down in the ECU.

For one of these reference voltages to be too high would mean either a fault in the ECU, or an electrical fault in a gizmo with both a 5v sensor and a 12v supply which is allowing some power from the 12v (battery supply) back into the 5v reference. Or less likely, a wiring loom short circuit.

The first test for this would be to measure the voltage present at the reference pin of all known sensors, to see if any do actually read high. Then to disconnect sensors to see if the voltage dropped back to 5v.

But the essence of this code is that it suggests an electrical / electronic problem, not a mechanical one. The caveat to this is that these codes are not always right, the software is (very!) fallible. But they are a starting point, and that is where I would start, but it might not be easy without wiring diagrams and some electrical testing experience. Clearing and re-reading codes a few times to see if the same code keeps coming back is also a good idea, in case it was just some glitch or side effect.

Sorry if that sounds a bit gloom-monger-ish, but that is what the only hard evidence is pointing to!

Thanks for the detailed response, I cleaned the EGR valve because I was so close to it while I was doing what I was advised by a garage, clean the multi connector by the diesel filter.  I done a scan on it using a better tool and it pointed towards a problem with that, multiple error codes all on the same loom, I just cleaned the EGR cause I hadn't done it before and I had removed majority of the parts in the way of it to get to the multi connector.

6 hours ago, BP2411 said:

I done a scan on it using a better tool and it pointed towards a problem with that, multiple error codes all on the same loom,

 

On 11/11/2018 at 9:20 PM, BP2411 said:

My car is now juddering on low revs, I thought at first it may be an air lock but I've done 150 miles since cleaning the EGR & it's still happening. 

Putting those two together does suggest a wiring problem in that area. Disturbing it for the connector & EGR cleaning may have made the fault go away for a while, but then bad connections usually come back worse after a while.

If the wiring is safe to get at with the engine running, you could move the wiring about while idling, and monitor for any codes that appear. If they do, clear them and repeat until, with luck and persistence, you might be able to narrow it down to one connector or bit of cable. I have done this sort of test quite a few times on various bits of equipment, though not car engines. I know it is not easy, so often you think you have it, then it changes and will not repeat.

When it comes to reading Ford DTCs, the best tool I have come across is Forscan, free software (for Windows), & around £16 for the ELM327 adapter. That P0643 is one I had not heard of before, that is one reason why I picked up on it. Does it re-occur, or was it just an odd one?

 

Since cleaning the EGR valve & cleaning the multi connector the EML hasn't come on, I haven't scanned it again as my friend with the expensive scanner is away, I'll scan with my Bluetooth one and see if anything shows.

My car started playing up again about a week ago, rough idle and juddering, ordered an odb scanner to hopefully get to the bottom of it, will post back if & when I get any error codes.

When I thought I fixed it I cleared the fault codes, now it's just saying engine malfunction service engine and not showing any codes.

I feel I'm talking to myself here but I'll update any way lol.  Just went to get fuel and halfway there the ! light disappeared and so did the engine malfunction message.

On 11/28/2018 at 12:06 PM, BP2411 said:

now it's just saying engine malfunction service engine and not showing any codes

There are a lot of manufacturer specific codes that do not show up on generic OBD scanners. The advantage of Forscan is that it is Ford specific, and will find at least 99% of all error codes on a Ford. It is practically impossible that a message will appear without a DTC to give some further information.

The disadvantage of Forscan is that it is not a self-contained system. You need a smart phone or laptop, an app or free software, and an adapter (ELM327). I can give more info if you want.

From the initial symptoms, it sounds like one of those annoying wiring or intermittent electrical faults that can take a long time to pin down. So really good diagnostic systems are a useful starting point, at least.

Is usb & a laptop the best option or will a WiFi adapter & the app on my phone be just as good?  I was going to post a seperate question today as it's really annoying me now.

These are the 2 I'm looking at, I know tunnel rat gets a lot of praise on here but I want it tomorrow (prime)

 

https://www.amazon.co.uk/Forscan-ELM327-config-diagnostic-HR-Tool®/dp/B076J44J3V

 

https://www.amazon.co.uk/Proscan-Automotive-Modified-Forscan-ELMconfig/dp/B07HGHSBH8

 

So wired & laptop or wireless & phone 

1 hour ago, BP2411 said:

So wired & laptop or wireless & phone 

If possible, go for the USB version. WiFi and CAN have some quite fundamental incompatibilities, it is not just the quality of the interface, some very clever buffering and intelligence is needed in the adapter to link these two protocols.

That said, a decent Wifi ELM should read and reset DTCs ok, but when it comes to recording live data, or doing any software uploads / downloads (eg ELMConfig) or critical operations (eg PATS programming) then I would go for USB every time. But if WiFi means you can keep the unit in the car ready to use at any moment if a light comes on, then that may be best for you. Prompt diagnosis can be a big advantage with intermittent problems.

TunnelRat sell on Ebay, and maybe Amazon, under the name Steve Elmer. They were one of the earlier outfits modifying and testing ELMs for Forscan, but I suspect all the ELMs come from China anyway, so there is no certainty their stuff is better than anyone else. The Proscan page on Amazon looks ok.

 

Wired it is, hopefully you're around tomorrow if it does pick up any codes.  Is it just a case of downloading forscan on my (wife's) laptop now? Is it a free program?

1 hour ago, BP2411 said:

Is it just a case of downloading forscan on my (wife's) laptop now? Is it a free program?

Yes:

http://forscan.org/download.html

The Windows version is free, and is the most capable. The phone Apps have limitations, and a small charge.

It is a bit quirky to use, but is reliable and safe (*). It does not install any dodgy stuff on your computer.

Here is a little guide to it:

https://www.fordownersclub.com/applications/core/interface/file/attachment.php?id=58645

* Note: Forscan is a powerful programme. It can erase your PCM, erase all your keys, and a few other drastic things, but you would have to try pretty hard to do that. These functions are in menus you are not likely to stray into, and it warns you and asks you before doing anything irreversible, even just clearing codes. Just read the screen, and if you are unsure of anything, just cancel.

Edited November 30, 20187 yr by Tdci-Peter
Add note

Wire arrived, forscan installed but all I'm getting is

checking Wi-Fi

No ELM found

 

I've tried it with the switch both ways & the car running and just ignition on.

Finally got it working and it's found 12 faults!