156 JTS Cat lambda faults + MCSF

[John Constantine 0]

Hi, I hope someone can help me with this. I've got a 156JTS that I use as my daily drive which has had the MCSF warning going on ever since I bought it last year.

 

I've cleared the fault codes numerous times; the light goes out and I get 20% better fuel ecconomy but after 3 days or so it's back on.

 

The fault codes pointed to the cats in the manifold failing so I replaced the manifold cats. No change. The light is still on, with fault codes now relating to the precat wideband O2 sensors.

 

Ive read on the other foums that this can be solved by hard wiring the sensors.

 

I tried this on one of the sensors, but the wiring from the car has 6 wires and the 02 sensor only has 5. One of the signal wires loops back in the o2 sensor block through a resistor and back out again. I've connected 5 of the wires back up but does any1 know whether the 6th wire is critcal?

 

The light is back on after dong this but the codes have not changed, implausible signal from the sensors, open loop errors etc.

 

Any suggestions asto what my next step should be?

[Joss 9]

Open loop means the circuit has failed. Probably because the wire is not connected in your case. It can also mean the component has failed as open loop on an airbag sensor means it's buggered in my experience. Smaky should be along soon to correct me and give more helpful advice!

[Smaky 73]

open and closed loop are normal operating arameters for these sensors if you are watching them on live data, open circuit is the one you have to watch out for and this is 99$ of the time down to a dodgy plug on the JTS, this can either have the wires glued into the back of the socket, be removed and hard wired or as I have always done and never had a problem with, just twist the pins in the soccket to create a more positive contact in the plug.

 

The other item which can cause this problem and is common on these engines is a coil pack failing, this will cause the precat of the cylinder to glow whilst running and is normally accompanied by a flashing MCSF light, if this occurs then sort it ASAP, your running on 3 cylinders, washing out the one which is not firing and cooking the precats which will eventually melt internally or worse cause something in its vacinity to catch fire as the cats are up at about 700'F when this happens.

[Joss 9]

Ah open circuit not open loop yes that rings a bell I knew what I meant

[John Constantine 0]

It's not misfiring, I would have mentioned it if it was.

 

The mcsf is back again but I might be getting somewhere with it now as she's gone down from 5 or so fault codes 2

 

P2243 lambda 1 upstream sensor fuel supply - no signal

P2254 lambda 2 upstream ground - no signal

 

The first fault code makes no sense to me. As for the 2nd one I'm going to try hard wiring this sensor to. Can anyone shed any light on the 5 into 6 wires issue?

 

Tia.

[John Constantine 0]

Problem solved.

[jhc 28]

What was the problem? If you don't mind me asking...

 

Always good to have the solution here in case anyone else has the same issues.

[Smaky 73]

I guess it what the dodgy plug issue.

[John Constantine 0]

Hard wiring the Lambda sensors changed very little. I'm still not convinced with this being a "fix" anyway as I've not been able to find an answer to the 5 wires from the sensor going into 6 wires at the loom issue.

 

In the end I fixed it by trading it in for an '07 plate Mondeo TDCi in black.

[Smaky 73]

Probably the sensor then but changing the car is cheating, on the other hand, good luck with the front springs and turbo.