V6 Fault code

Powellct · Post by **Powellct** » Mon Jan 03, 2022 4:51 pm

Afternoon all..

Have a flashing HOLD light - can I just check my reading first: long flash, 1 short flash; long flash, 2 short; long flash, 5 short; long flash, no flash = P1250?

If thats right, it points to the PRC solenoid, located in the most inconvenient area for testing.
Nonetheless, test I have - continuity through coil, clicks when connected to 12v, 12v at correct terminal, and continuity to term 4J on the ECU (which is what it should be according to the manual). Also relay under bonnet testing OK.

Seems that particular solenoid is for hot starting? Any ideas where the ECU signal to term 4J comes from? Logic would suggest a temp sender somewhere as the criteria is 90C coolant, 50C engine bay, but the main gauge works fine.

Tried the "disconnect battery 20 seconds, press footbrake" too.

Hair pulling time.

Post by **g8dhe** » Mon Jan 03, 2022 5:48 pm

The Pressure Regulating Valve (PRC) controls the fuel pressure I believe, the solenoid is driven from the ECU computer, it gets the relevant info from what ever sensors the software has been written to use usually several including the engine coolant temperature and incoming air temperature. The solenoid then controls the fuel flow directly. Following the diagrams around the valve seems to open the path to the Fuel Return system see the diagrams http://www.lushprojects.com/bongopartsm ... mgno=.html the PRC valve is centre right.

Powellct · Post by **Powellct** » Mon Jan 03, 2022 6:27 pm

Cheers Geoff,

It isn't actually the PRC the fault points to, it's a little three port solenoid at the back between the two banks - two vacuum pipes, a vent to atomosphere via a filter and a 12v supply, the ground side controlled by the ECU.
All the testing per manual comes back OK, as far as ECU pin 4J. Said solenoid takes its signal (apparently) from the coolant temp ≥90°C and the engine bay temperature ≥50°C.
I guess the next step is to find and test the engine bay sensor, although I would have expected that to throw up a fault code?
Whatever it is it's not engine running specific, as the fault come up as soon as ign on.

Post by **g8dhe** » Mon Jan 03, 2022 7:00 pm

Slightly confused then! The 4J terminal drives the PRC, the error report says its the PRC, but your saying another vacuum valve is the problem ? If so which one ?

Powellct · Post by **Powellct** » Mon Jan 03, 2022 7:14 pm

Ah, I can see the confusion - as far as I can see there's no electrical connection to the PRC - the solenoid is separate.

Powellct · Post by **Powellct** » Mon Jan 03, 2022 7:23 pm

This is the test process which proves out.

Post by **g8dhe** » Mon Jan 03, 2022 7:50 pm

The item you have circled is the PRC and is just a simple valve operated by the solenoid. Which is the three port one you refer to ?

Powellct · Post by **Powellct** » Mon Jan 03, 2022 8:22 pm

This little beastie

Post by **g8dhe** » Mon Jan 03, 2022 11:03 pm

Ah we may be looking at different things here!
See here http://www.lushprojects.com/bongopartsm ... 1of03.html
18-741C (no.1) top right is a vacuum solenoid valve which is what your pointing out, which is part of the EGR system.

Whilst I'm looking at 13-280A top right here http://www.lushprojects.com/bongopartsm ... mgno=.html which is the Petrol Regulator Control valve and controls the flow of fuel.

The vacuum valves are well known for failing usually the plastic tubes crack or the piping around them they are easily available on eBay I believe https://www.ebay.co.uk/sch/i.html?_from ... 1&_sacat=0

Powellct · Post by **Powellct** » Tue Jan 04, 2022 7:19 am

Getting there then, Geoff! I did wonder how it would throw a code up. However, the manual refers to it as the PRC solenoid, not EGR.
I'll have the centre off today then and check the pipework, pain in the backside - there's two of the buggers and both test OK. I'll have a look at the engine bay temp sensor too.

Post by **g8dhe** » Tue Jan 04, 2022 10:32 am

There are two of them and they have different part numbers but have the same diagram numbers! I wonder if there is a mix up with naming on the diagrams ?

Powellct · Post by **Powellct** » Tue Jan 04, 2022 11:38 am

There are indeed two - but only one test procedure for the vacuum path, so I assume thats for both... May try swapping them over. The centre (more forward one) energises on ign on, the rear one is the one controlled by the ECU pin 4J. I'll check all the hoses, but a cursory glance yesterday didn't make me think they would be bad, and certainly the hose stubs are sound.
Was awake at 04:30 going through mental wiring diagrams - its been over 20 years since I was in the trade!
I'll double check that fault code too, just in case.

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