fault codes on 2005 3.0 V6. Can’t have all faulty, surely? Codes reappear as soon as deleted. Any ideas please

P0131 universal heated exhaust sensor, circuit low-voltage, bank 1 sensor 1

P0151 universal heated exhaust gas sensor circuit, low voltage bank 2 sensor 1

P0031 universal heated exhaust gas sensor, heat control, circuit low bank 1 sensor 1

P0051 universal heated exhaust gas sensor, heat control, circuit low bank 2 sensor 1

P0036 heated oxygen sensor, heater control circuit bank 1 sensor 2

P0056 heated oxygen sensor, heater control circuit bank 2 sensor 2

 

Check you have power at and through fuses 33 and 34 (30Amp each) in your front power distribution box when engine is started.
They supply power to all your HO2 sensor heaters.
If no supply to those fuses then check relay 12 is functioning (HO2 relay), could be bad coil or contacts in relay.

 

Agree with h2o2steam , the crucial hint appears several times: low voltage, circuit low.

Most likely you have a ground problem. Therefore, check the ground straps between the engine and the body and especially the ground point G2 on the front right (in the direction of travel) behind the headlights, they tend to corrode. You can also try replacing the relay 12 in the engine compartment for the supply of the O2 sensors with another one.

Fritz

 

Rerlay 12 'unserviceable' it seems....Checking wiring diarams late last night isn't G30 the ground for 02 sensors rather than G2?

 

Before we try to solve the possible R12 relay replacement issue....did you have 12 volts getting to Fuses 33 and 34?
If you do have supply to those fuses, then R12 is OK.

Looking at the schematic either ground 26 or ground 30 are likely involved in the HO2 sensors operation, which are behind respective front shock towers.
The grounding post can be problematic and fragile into the aluminum bodywork.....lots of comments and issues generated by various grounding points in these cars.

 

No power to fuses 33/34, so guess it’s a relay issue. Which is unserviceable

 

The way I see it, you have two options if the system relay is "kaput".

1/ Comprehensive repair:
Removing and disassembling the front power distribution box to reveal the two "sandwiched" circuit boards that make up that assembly.
The relay's solder terminals will be inaccessible as they will be in the narrow void between the PCBs so if you are determined to remove and replace the failed relay you need to separate the boards to access the relay terminals.
The easiest way to do this is to use some fine side cutters or a Dremmel with a fine cutting wheel and nip or slice each of the 100+ interconnecting pins that link the two boards together. Note the orientation of the boards so you can marry them back correctly.
It is best to cut the pins at their mid-point as you want to maintain some accessible pin real estate for both halves.
Once you have the boards separated you have full access to replacing the relay.

Now there are two schools of thought for putting the boards back together.....
A) Either you can simply butt the links and bridge over the cuts with solder or a soldered sleeve like some fine brass tubing or strapping. Solder alone may eventually develop a fracture at the joint over time with vibration, so adding some bridging material would be more robust.
B) Pin extraction and replacement is a tedious job and requires a good capacity soldering iron. The factory pins are square shafts and also a friction fit into the PCBs so they do not move during the manufacturing process. The boards are double layers (copper on both sides of each PCB) and the copper tracks are generous and with the fibre glass PCB substrate tend to soak away the heat of smaller soldering irons, so you want to be using a 60+ watt iron at least to make the job faster and decrease the chance of delaminating the board with long duration heat contact. You will be heating the pins with the aim of activating the solder on both sides of the board while pulling the pins with some needle nosed pliers they are a tight friction fit. The piers will eventually heat up as well and it is a tough job.
I did this method on the rear power distribution fuse box of my XJ8 and used some brass rod to fully replace the pins, but in hindsight I might have opted for cutting and bridging pins instead.

2/ Sympathetic repair:
Rather than trying to separate the two PCBs to physically replace the relay, you can effectively add a relay in parallel to the failed one (even if the original relay decides to occasionally work it won't make any difference as you will be isolating the output at the OEM 30 amp blade fuses anyway). First you need to find a suitable rated relay not only for capacity but also one whose coil will accept long period of continuous energizing. Not all relays are built the same, some are fast acting but have short duty cycles, while others are made for long periods of sustained operation (headlight relays etc). You'll need something that is around 50-60 Amp rated seeing you have two 30 amp fuses it is supplying.
Once you have found a suitable relay you will also need some aftermarket 30 amp fuses and carriers as you will likely not be using the original fuse locations to carry a functional fuse anymore.
You should be able to easily identify and intercept the coil drive wire from the schematic and splice into it to take a drive to your new relay coil.
Add an additional earth to the grounding point to complete the coil circuit.
Pick up a unfused 12 volt feed from a input wire or terminal to supply your common pin of the relay.
As for the output, you will be using the normally open (NO) pin of the relay as the output via you two new 30 amp fuse assemblies and can either simply tap into the relevant output wires leaving the power distribution assembly, or inject back into the appropriate side of the now redundant OEM blade fuse carrier sockets by exposing some additional pin material and soldering onto the back of a donor fuse.
It is then simply a case of securing your replacement relay, tidying up the new wiring routes and making sure everything is well secured and insulated.

Hope this helps.

 

extremely helpful, and very informative. I will have to put my big boy pants on and make a decision on which way to go next

 

Is the Jag drivable?

 

Have you checked for power to the relay coil circuit when the engine is running?

 

I had similar codes relating to o2 sensors. After replacing all, fuel pressure sensor, new maf, I still had the codes. I decided to take the plugs out to check for fowling. One of them was leaking past the ceramic and misfiring.
I fitted a new set of plugs and all codes disappeared.

 

Bizarre !

 

We do have same trouble with a x356 Daimlersuper eight
one cat shot we replaced it with two second hand ones with their o2 sensors. Result after 30 km driving switch of engine , start again then P0131 P0134 P0151 P0154
we kept the old cats and sensors so going back to original sensors soon.
I will have look for the dground studs. Check Airfilter clean Maf. Look for leaks with my vaporiser.
car runs fine for some time then has a shutter
So maybe coils

 

On the Daimler with the secondhand cats from U s Model vanden plas with its catalysers. . We seem to have found a couple of problems After been annoyed with P0131 P0134 P0151 and P0154.
.
Airfilter dirty as hell fasteners on rubbertube inlet from airbox not tightened and not tightened on the aluminum inlet.
by taking that xjr duct of to inspecct it. Underneath was a gummed up halvway closed plate with dark silicone matter. Taped right now to have it almost airtight. Lets try to get a new one

 

So check for airleaks first after 17km test drive faults did not reapear hpe it stays like that