The dreaded engine light - 939 2.2 JTS

[ACE]

MES reports:
"P2414 - Lambda sensor 1 upstream (plausibility)"
("Plausibility"? like it's having a bet each way ... ?)
"P2237 - Lambda 1 sensor upstream (current)"

Question 1:
Does "upstream" refer to one of the "pre-cat" sensors, rather than a "post-cat" sensor?

eLearn provides instructions for replacement of:
"Left Upper" Lambda sensor; also referred to as the "Lambda sensor on the pre-catalyser" ... Note no number;
"Right Upper" Lambda sensor; also referred to as the "Lambda sensor on the pre-catalyser-2" ... Note use of "2"

Question 2:
Does MES's "Lambda sensor 1 upstream" therefore relate to eLearn's "left upper"?

eLearn also has separate diagrams showing the location of the four sensors.
Sensor K015: the "left upper" Lambda sensor
Sensor K016: the "upper right" Lambda sensor
Sensor K017: the "left rear Lambda sensor ... on the catalytic converter"
Sensor K018: the "right rear Lambda sensor ... on the catalytic converter-2"
The use of "rear" seems to be a synonym for "post-cat".

These diagrams also show the location of the relevant connectors indicating that the "uppers" use a wide flat connector, whereas the "rears" use a compact "D" shaped connector.

The use of "left" & "right" coincides with the relevant location of the pairs of sensor connectors on the firewall. While this is useful, they may be named so for a different reason.

Given the above, it seems that I need to replace the unnumbered pre-cat Lambda sensor, I.e. the left upper which according to the diagrams should have a wide flat connector.
BUT!
All images I can find (on the web) of the pre-cat Lambda sensors suggest they they use the "D" shaped connector (which is what my parts supplier has delivered).

Question 3:
If Q1 & Q2 are both "yes", what did I miss?

[GTVeloce]

I bet you don't have this problem with your GTV6!

Not really helpful I know but just trying to convince you to drive your GTV6 more, or sell it to me 

[Citroënbender]

Unplug the sensor you suspect it is, and see what further faults are logged.

[ACE]

CB, good idea! Thanks. I will and will report back ... but it may be a day or two.

GTV:
Absolutely correct!
1700+ km in 5 days - who else drives one that much?
You may have a long wait ... ;-)

[ACE]

OK, with all codes cleared:
Disconnected the terminal that I suspect belongs to the errant sensor;
Started the engine - no engine light! Switched off anyway.
Checked for codes again:
P0135 - Preheating resistance 1 above catalyser

Different code but it seems to be pointing to a problem with the same sensor "1 above catalyser" ... ?

Cleared codes again.

Reconnected terminal and disconnected the terminal that eLearn indicates is the one.

Started engine - again no engine light. Switched off.

Checked codes again. This time nothing!

Time to start swapping bits out methinks. Starting with my hunch.

Cheers.

[bazzbazz]

Q1 - Upstream DOES mean pre-cat

Q2 - Facing the engine from the front of the car it should be -

       #1 is for the left bank (drivers side - Cylinder 1 & 2)
       #2 is for the right bank (passenger side - Cylinder 3 & 4)

But as said, disconnect each sensor and it will show up on MES and confirm.

[bazzbazz]

It will most likely be the connector pins not making good contact, as you unplug/replug the connect it changes the contact fit.

May I suggest unplugging the connector and using a pair of forceps or fine needle nose pliers twisting the male pins in the plug slightly so that when plugged back in the female pins, they will be a tighter fit.

If the problem persists or returns at a later date replace the Lamba Sensor and its plug.

[Craig_m67]

Sildenafil pliers (blue handles) are perfect for this type of older connection issue...

[Citroënbender]

Aah yes; the small ones with a lozenge-shaped handle. 

[bazzbazz]

Could everyone PLEASE Google Sildenafil pliers and see what comes up . . . .PLEASE!   
(It does involve tools, but not the ones you'd think)

[ACE]

Thank you all.
I'll try the "tweaking" trick before I swap sensors, but maybe not with the recommended tool!
I have tried tweaking terminals when attempting to bring the oil temperature gauge back to life - to no avail :-(

Bazz, I don't like to challenge a respected and acknowledged guru, but the eLearn diagrams indicate that left and right refer to the car's sidedness, not our handedness as we poke about under the bonnet :-(  But this may also be the cause of the apparent contradiction in eLearn ?

Cheers :-)

[ACE]

Attached are the page from eLearn and a photo of the area where the lambda connectors reside.

eLearn indicates the target is third from left, but it has the wrong type of connector :-(

[bazzbazz]

I am referring to what MES indicates, not what eLearn is indicating.

MES refers to Lambda Sensor 1 & 2, as said before, Sensor 1 is for cylinders 1 & 2 and Sensor 2 is for cylinders 3 & 4.

Upstream is the Pre-Cat Sensor, downstream is the Post-Car Sensor.

So if you have a fault with Upstream Sensor 1, as you face the engine from the front it is the Sensor on the left Header before the Cat.

If you have an error with Downstream Sensor 2, it is the right hand header Sensor after the cat.

As for which is the correct plug on the firewall, just follow the loom back from the indicated sensor.

[ACE]

Many thanks for the clarification Bazz.
It seems I have been focussing on the wrong target :-(

[ACE]

Update:

Background:
Subject: 4 cylinder, 2.2l JTS motor
Error: P2414
Cause: potentially dodgy Lambda sensor

Lessons learned:

Topology:
! there are two heat shields covering the exhaust and catalytic converters between the engine and the firewall.
! there are two catalytic converters (cats) nestled beside the motor, in a plane parallel to the motor's longitudinal axis.
! the exhaust manifold pairs cylinders 1 & 4 and separately cylinders 2 & 3;
Each pair (bank) leads to a single catalytic converter

! Convention decrees that the bank that cylinder 1 flows into, is "Bank 1"
The cat in Bank 1 is therefore Cat 1.
! For this engine (others may be different!) Cat 1 is fed by Cylinders 1 & 4
The corollary is that Cylinders 2 & 3 feed into Bank 2 & Cat 2.
! Cat 1 is spacially closer to Cylinder 4 and the left side or the car!
(Cat 2 is closer to Cylinder 1 and the right side of the car)
! there are four Lambda sensors, one at the head of each cat (pre-cat Lambda sensor) and one at the tail of each cat (post-cat Lambda sensor)
! pre-cat sensors and post-cat sensors are different (and utilise different types of connectors!)
! three of the Lambda sensors can be (relatively) easily attacked from underneath the car/engine, but one is best dealt with from above.

The challenge:
! P2414 relates to Bank 1 / Sensor 1. I.e. the pre cat Lambda sensor on Cat 1

! This, of course, is the most difficult to access!
! eLearn says (I paraphrase) Unclip the sensor cables & Remove the sensor. However, it's a bit more involved ...
! The pre cat Lambda sensor on Cat 1 requires removal of the top heat shield and, at least, the loosening of the second (lower) heat shield - so that it can be pushed aside. It can't be removed without removal of the Lambda sensor first! Catch 22 ?
Channeling eLearn: the Lambda sensor can now be removed! (I used a crows foot socket on the end of a series of short wobble bars - to get around some corners).

Then, all that should be required is to pop the new one in, reassemble it all, and test.

But the problems have not yet gone away!

After some unrepeated (spurious?) errors, the new issues being reported were an occasional, but consistent, P0300 & P0302 (ignition failure) with a rarer P1175.

btw: A compression test confirms even pressures across the four cylinders.
160 psi dry and 185 psi wet +/- a couple of psi.

New spark plugs and cleaning all the coil contacts made a little difference - maybe just a reduced occurrence of the issue - but still frustratingly frequent.
However, the improvement was more likely due to the repair of a small crack in the bellows between the AFM and the throttle body! The repair is effective, but temporary, while a new one wings it's way from O/S.

So, as it wasn't a plug causing the P030x, the coil pack was the next suspect.
(It's a four coil rail, so you can't swap individual coils - to test for a dud - the whole rail has to be swapped!)

The replacement coil pack made a little difference! Or was it imagination ...
Still P0300 & P0302 (ignition failure) with a rarer P1175.

Symptoms now include running a little rough when cold, and some slight hesitation at low to mid range rpm. Otherwise the engine light occasionally flashes (it does not stay on permanently) most often when the engine is under load and at low to mid rpm. When it clears its throat it still spins and pulls nicely.

So, are the injectors the next in line for attention, or is it possibly something altogether different?