Calling all Fuel Injection Experts!! D2A V8 O2 Sensors

[jskerm]

Hi all, as the title suggests I am at wits end again with my Discovery 2 V8.

The problem so far......

I have recently rebuilt everything in this car including diffs, transfer case, and the entire engine. The engine was fully rebuilt, tophatted, heads done, all mickey mouse.

After firing the engine up and driving for a few months I noticed that the vehicle always smelt 'fuelly'. I plugged in a Lynx diagnostics system and It came up with a myriad of O2 sensor faults. Lots of them would have been there long before I rebuilt the thing. Long story short I have ended up replacing both O2 sensors with Bosch units (AU Falcon Style), and the connections going to them. I have checked wires for continuity right to the ECM and have checked fuses in fuse box. Everything checks out OK.

I have also reset ECM adaptations each time I have fiddled with something.

The problem now is that the left hand Bank (bank 1) just will not work correctly. It sits on about a .45 to .58 V O2 sensor reading (from the Lynx diagnostics) and just sits there. The RH bank (bank 2) works as it should and alternates above and below the mid range voltage (.45 V I think)

The fuel trim on the RH bank goes up and down. The left just sits.

MAF reading is from 20 kg/hr up to 300 odd when you boot it.

The engine runs fine, bit low on power and still smells a bit fuelly.

I have swapped the spark plugs from Left Bank to Right and vice versa, the plugs all looked the same (nice Burn) and the problem stayed with the left bank.

I will always get the following codes about five minutes after staring.

O2 probe heating before Catalytic converter-Minimum Value Not Reached. Fault present and Static

O2 probe pre catalyst - signal missing. Fault present and static.

On a few occasions I have got the thing to go into closed loop running. When it does it lowers the left bank to minimum fuel trim, and the engine runs like a bag of snot. When this happened it also logged the following code.

Fueling adaption ti multiplicative, minimum value not reached.

All symptoms point to a failed O2 sensor, but when you swap sensors from side to side the problem stays with the LHS. So you would then assume a wiring problem, but I have renewed both connectors and the wiring is OK from the sensor to the ECM (checked with multimeter continuity tester)

The signal wire to the ECM (input) is connected to the black wire on the O2 sensors, and the earth to the grey. There is 14V from the ECM for the heaters.

I am out of ideas. Short of replacing the ECM or burning the thing to the ground I am unsure where to go from here. I think the fact that only one side is playing up rules out the MAF sensor.

Would a stuffed catylytic converter have an effect on the operation? Looking at the LH down tube the LH bank has been running rich for a while..

Any advise or thoughts would be greatly appreciated as I am starting to type 200 series Land Cruiser into carsales.com a bit to much for my liking lately....:o:confused:

[bee utey]

Make a test rig with a spare O2 sensor, see that the 14V heater voltage is present at the sensor with it plugged in and drawing current. Your adaptor cable may have a dodgy joint. They should never be soldered. I use special small uninsulated crimps then heat shrink the joints.

[PhilipA]

I know it is pretty basic, but have you checked the continuity of the circuit between the ECU and the LH O2 sensor.
I take it you have crimped the leads if they are Falcon O2 sensors as the stainless stuff is hard to solder.
So my advice is to just check the continuity.
The other possibility is that the earth return for the O2 sensor is poor on the left bank. If they are 2 wire sensors the earth return is via the exhaust pipe presumable to the head . This may be poor on the LH bank so maybe run an earth wire from the manifold to the head.
Regards Philip A

[jskerm]

Make a test rig with a spare O2 sensor, see that the 14V heater voltage is present at the sensor with it plugged in and drawing current. Your adaptor cable may have a dodgy joint. They should never be soldered. I use special small uninsulated crimps then heat shrink the joints.

I purchased a tail from the AU falcon harness with the sensors. This means the wires are solderable which I have done. There is no cutting into the original sensor harness as it plugs into the new AU style plug. In saying this, I will check it at the sensor itself like you say.
The fact that the sensor registers a voltage soon after starting indicates that the heater is working, but seems to want to log a fault.. Just like if the sensor is returning a voltage that varies between .45 and .69 volts, there must be some sort of signal returning from the sensor... It just won't register it and make the fuel changes..

[jskerm]

I know it is pretty basic, but have you checked the continuity of the circuit between the ECU and the LH O2 sensor.
I take it you have crimped the leads if they are Falcon O2 sensors as the stainless stuff is hard to solder.
So my advice is to just check the continuity.
The other possibility is that the earth return for the O2 sensor is poor on the left bank. If they are 2 wire sensors the earth return is via the exhaust pipe presumable to the head . This may be poor on the LH bank so maybe run an earth wire from the manifold to the head.
Regards Philip A

The wires were soldered into a replacement AU harness tail. The sensor wires themselves have not been cut and are in their original connector. I have checked continuity from the new plug, to the ECU plug. All good and wired correctly.

They are a 4 wire sensor so the earth is through the wiring harness. This has been checked for continuity to the ECU plug as well. I have the black wire from the sensor attached to the signal wire to the ECU (blue or orange depending on which side) and the grey wire attached to the red/black earth wire. Is there a way of testing the earth into the ECU? I have checked the continuity but only to the plug into the ECU

[ashhhhh]

Its generally considered bad practice to solder o2 sensor connections.
I would buy new ones with the connector attached if I were you. I got mine from Amazon for $45 each.

Your symptom of one bank showing no activity is exactly what I struck with mine.

I had;
P1000 = LAMBDA SENSOR UPSTREAM
CATALYST BANK 2 DRIVE CYCLE C
OCCURED 7 TIMES
SIGNAL INVALID
FAULT IS CURRENTLY PRESENT
FAULT DETERMINED AS INTERMITTENT
FAULT DOES NOT CAUSE THE
MIL LAMP ACTIVATION

---
P0175 = MIXTURE ADAPTION FACTOR
FRA BANK 2 DRIVE CYCLE C
OCCURED 1 TIMES
SIGNAL TOO HIGH
FAULT IS CURRENTLY PRESENT
FAULT DETERMINED AS PERSISTENT
FAULT DOES NOT CAUSE THE
MIL LAMP ACTIVATION

I replaced o2 sensors, MAF, checked wiring etc.
It turned out to be caused by an air leak at the inlet manifold joint, probably injector o-rings too.
Sorted all that, no more issues.

[jskerm]

Its generally considered bad practice to solder o2 sensor connections.
I would buy new ones with the connector attached if I were you. I got mine from Amazon for $45 each.

Your symptom of one bank showing no activity is exactly what I struck with mine.

I had;
P1000 = LAMBDA SENSOR UPSTREAM
CATALYST BANK 2 DRIVE CYCLE C
OCCURED 7 TIMES
SIGNAL INVALID
FAULT IS CURRENTLY PRESENT
FAULT DETERMINED AS INTERMITTENT
FAULT DOES NOT CAUSE THE
MIL LAMP ACTIVATION

---
P0175 = MIXTURE ADAPTION FACTOR
FRA BANK 2 DRIVE CYCLE C
OCCURED 1 TIMES
SIGNAL TOO HIGH
FAULT IS CURRENTLY PRESENT
FAULT DETERMINED AS PERSISTENT
FAULT DOES NOT CAUSE THE
MIL LAMP ACTIVATION

I replaced o2 sensors, MAF, checked wiring etc.
It turned out to be caused by an air leak at the inlet manifold joint, probably injector o-rings too.
Sorted all that, no more issues.

When this happened to you Ashhhhh, was it reading a voltage like mine? or was it either to high or too low? the thing that confuses me is if it is an air leak or similar, wouldn't the voltage be reading right down low indicating its too lean on that bank?? Mine is varying between .45 and .69 V

[jskerm]

Its generally considered bad practice to solder o2 sensor connections.


PS, I have only soldered the AU plugs into the land rover engine harness. All wiring for o2 sensors has not been touched from new, as in they came with AU plugs installed.

[ashhhhh]

I dont recall actual voltages but the symptom was that one bank fluctuated a lot and the other was very low and basically static. (like 0.15 low)

So yeah, your right - lean in my case.

Do you have any P codes to go with those descriptions?

[PhilipA]

I wonder if it is one or more crook injectors.
Regards Philip A

[jskerm]

I dont recall actual voltages but the symptom was that one bank fluctuated a lot and the other was very low and basically static. (like 0.15 low)

So yeah, your right - lean in my case.

Do you have any P codes to go with those descriptions?

No P codes, the lynx setup only puts a two or three digit number beside the fault, I can't remember the numbers but will post them next time I hook in.

[jskerm]

I wonder if it is one or more crook injectors.
Regards Philip A

This is what I was thinking when I checked the spark plugs. I would presume a crook injector would mean unburnt fuel, giving the slightly rich reading, but all spark plugs looked dry and a nice burnt grey colour. Maybe I should change injectors from side to side and see what happens...

[bee utey]

PS, I have only soldered the AU plugs into the land rover engine harness. All wiring for o2 sensors has not been touched from new, as in they came with AU plugs installed.
Ah, yes, I'd assumed that you soldered the AU harness plugs to some chopped off D2 sensor connectors. I made (crimped) adaptors this way so the OEM D2 wiring remained untouched and could use stock O2 sensors at any stage in the future.

Anyway, if the heater current is insufficient to bring the sensor up to operating temps quick smart, the sensor will output but at a lower voltage than optimal. A too cool sensor may also get some voltage leak across from the heater winding, old sensors can get quite bad in this respect. Moisture from the initial fuel burn may condense inside the sensor until it gets up to the correct temp. In the meanwhile the ECU has logged a fault and disregards the sensor.

[jskerm]

So I got the missus to drive the car into town today. 120 km round trip. I cleared all codes before she left and reset the adaptations. Upon her return she said it ran very well...

It had re logged the signal missing fault for the LH bank, but also a o2 sensor heater minimum value not reached fault for both sides.......

In the live data the RH bank was still operating perfectly, whilst the other side just sat at .475 V.

Does anyone know a way I can test the earth for the heater circuit and sensor output earth? These are earthed in the ecm but does that mean they are also earthed to the vehicle chassis. Just wondering whether I can check continuity between the chassis and the earth wires at the sensor to prove earth side is ok.

It boggles me to think that it might be a vaccuum leak or injector, as it is reading too rich when it does change. It just won't "flip flop" like it should.

Seems you can get into a low km GX 200 series for around 40K now....:p

[ashhhhh]

Yeah I think you're into something with the ground theory, 0.45 (or so) is the "cross over" point between rich and lean, and also the default state in the case of signal or earth failure.

Can't help much locating the correct earth, maybe RAVE will help?

[jskerm]

Victory!
Wasn't an obvious one though. Checked the earth from the left hand sensor and found it was grounded to the chassis. Checked the RH one and no earth. Checked the wire right back to the ecu and still no earth. The pin for the rh earth in the ecu was grounded, the left one not grounded.
After pulling the Ecu apart and following that circuit i found a point where the ground came back again on the circuit board, luckily it was near a solder joint, put a dab of solder on it and bingo, earth back at the pin.
Anyway, after putting it all back together both sensors now work beautifully.

Goes to show theres always a solution to every problem, and if anyone is in the market for two perfectly good o2 sensors that i thought were stuffed, give me a pm!

Thanks everyone for your help.

[ashhhhh]

Good news!

[jskerm]

For those that are interested, repairing the o2 sensors has given me an extra 100 km per tank. Worth the hassle.

[ballbag]

Well done.

What sort of mileage are you getting?

[jskerm]

About 500 km a tank. Was struggling to get 400 before.. Goes better too.