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307 hdi 136 recurring P2122 error - intake air heating solenoid short to earth

Posted By tmead Saturday, June 07, 2014 4:55:44 PM
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307 hdi 136 recurring P2122 error - intake air heating solenoid short...

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tmead
 Posted Saturday, June 07, 2014 4:55:44 PM
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The car is a 307SW hdi 136, engine code RHR, on an 05 plate

This seems to be an intermittent fault, but has happened several times over the last month. It pops up an antipollution message, and reports on planet as P2122 permenant fault: intake air heating solenoid short to earth . It does not put the car into limp mode, but does knock off the cruise control.

Googleing reported a couple of pages where there is supposed to be a 'heater matrix' type thing under the air filter housing. I can't see anything like that anywhere around the air filter housing, and there is no indication of coolant pipes heading that way at all. I'm inclined to discount this.

The full fault description page on planet (F6) shows:

ECU Fault code P2122
engine speed 1504rpm
measured injected flow 44.18mg/impulse
coolant temperature 81 degC
vehicle speed 84 kph
battery voltage 14.35V
engine status engine under load
time elapsed since ignition positive 572 s
bypass butterfly solenoid valve OCR 6%
EGR throttle electrovalve OCR 51%
measured airflow 360 mg/impulse
airflow setting 376 mg/impulse
intake air temperature at the air flow sensor -50 degC
inlet air temperature at manifold -50 degC

now I don't know about you, but -50C seems a pretty odd reading to me, based in the UK in May/June ? live data shows a pretty normal value now, +37, which seems fine a while after a short trip.

I'm not sure why both these values could be so wrong together - it does seem odd. Assuming one comes from the MAF and one from the manifold temp sensor ? I'm reluctant to head off to change the MAF on the off-chance, but maybe its better to start with the temp sensor because its cheaper ?

All help and suggestions about this issue welcome !
Robski
 Posted Saturday, June 07, 2014 5:09:43 PM
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now I don't know about you, but -50C seems a pretty odd reading to me
what version of PP ?

what does service box reveal for the DTC ?


I'm reluctant to head off to change the MAF on the off-chance
what's wrong with testing ?


Rob.
K And R
 Posted Saturday, June 07, 2014 5:14:27 PM
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Rob

x 2

tmead

do you have a wiring diagram ?

Kev.

ps No outcome on your other thread, do you deserve any help ?


"If you dont KNOW how it works, don,t try to test or fix it"
Saturday, June 07, 2014 5:21:14 PM by K And R
Tismot
 Posted Saturday, June 07, 2014 5:14:35 PM
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>>> I'm reluctant to head off to change the MAF on the off-chance, but maybe its better to start with the temp sensor because its cheaper ? <<<



You should not be rushing off to play parts darts with regard to either.



You have done the EASY bit of plugging in a scan tool, NOW starts the skilled part of understanding the system and carrying out your testing / proving in a logical methodical manner.



Mark


Modern cars, Its all wizardry and witchcraft
tmead
 Posted Saturday, June 07, 2014 7:22:56 PM
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Thanks for your suggestions. I'll try to add some further info in response.

Robski - I'm not able to check which version of PP right now. Would it make a difference ?
I've not found an accessible area on servicebox that shows details of DTCs. If this is available without subscription I'd be grateful for your pointers about where to access this part of the site.

I'm open to ideas about what to test, but whenever I've connected to the car, live data shows reasonable results for both temperatures. I will measure resistances tomorrow, but given the sensible live data, do not expect them to be particularly odd.



K and R
I don't have a wiring diagram.
You are correct - no resolution on the dash lights issue described in a previous thread. A very occasional intermittent fault, where checking earth points, connector cleanliness and continuity of cabling all showed no faults. It has now not occurred for 4 months at least.



Tismot
I do not want to play 'parts darts', so thought I would consult some people who may know whether it is even appropriate to ignore the description of the code, which involves a solenoid short, and focus on two very strange temperature values in the error log ?


I can take some readings from the temperature sensor and MAF tomorrow (assuming that this is the right area to be looking in)




Angus
 Posted Saturday, June 07, 2014 7:24:53 PM
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tm

As the only reason, that I can think of, to increase the temp of a diesel's intake air would be to assist a DPF regen, is this solenoid operating an intercooler by-pass valve?

If so, is it live-fed - and is that feed functional?


.
tmead
 Posted Sunday, June 08, 2014 4:07:31 AM
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Now that's an interesting idea - I think there is an intercooler bypass. Never thought about that as a 'heater', but it does fit well. Doesn't tie up with the -50C readings, but gives another avenue to look into.
I'll check the solenoid later.
K And R
 Posted Sunday, June 08, 2014 4:22:04 AM
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tmead

"If this is available without subscription"

Do what we all do, subscribe and you will have the info needed and you can even look up the wiring diagram's you will need to do correct testing.

Kev.


"If you dont KNOW how it works, don,t try to test or fix it"
Timbo
 Posted Monday, June 09, 2014 3:33:01 AM
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These do have the intercooler bypass, for regen reasons, you should be looking here.

On a knife edge !
tmead
 Posted Monday, June 09, 2014 4:34:45 AM
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There are two solenoid valves, each controlling a seperate air direction flap in a 'doser' unit. One of these would open/close the bypass. They both measure the same, 16.4 ohms, and the connections look clean and dry, no damage to the wiring or shorts to earth in the wires.

The DPF loading is showing as 55%, so I'm not sure it would be trying to open the bypass for regen yet, but it seems that the bypass is opened at startup to raise engine temperature quicker, and then closed to use the intercooler for normal running. Could be that the solenoid fault was registered when the ecu energised it to try to close the bypass.

Still confused by the -50C temperature readings, the temperature sensor in the inlet manifold was covered in gunk, but reading 8-9Kohms, which I believe is normal for around 20C. MAF temperature sensor not yet checked, but each time I look at live data it shows the two sensors within a few degrees.

Back to the day job, so not much time to investigate further at the moment.

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