Lambda sensors

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8

800jimbo

New Member
Posts
59
Location
Winchester
2000/X P38 4.6

Following on from my other tickover thread, I put my car in to a garage as it was running badly especially on LPG and stank at tickover.

Garage have replaced the MAF and report it's much better, but the ECU is not communicating with the Lambda sensors. They asked whether it has ever been chipped as they could not fathom the problem.

I assume the garage thinks the lambda sensors are not faulty in which case:

Would there be any point / is there any history of Range Rovers being chipped which involves breaking communication with the Lambda sensors?

Does it matter overly?

If it does, WTF do I do now???
 
I picked the car up today and it is better. Apparently there is just no input registering from the lambda sensors. The garage replaced one with a new one but still no input. Apparently next step would be to get the ECU checked to see if there is a physical fault or whether the lambda sensors have been programmed out by someone for some reason.

Anyone come across this before?
 
Its probably nothing to do with the oxygen sensors... More than likely a low reading maf keeping the injector pulse widths so narrow the ecu cant get the mixture rich enough for them to switch up rich.
 
Fault code says O2 sensor communication inactive both banks, and the MAF was changed with the fault present with both MAF's, so it does really seem to be a lambda communication issue.
 
What readings do you get from the maf ? You need 22-25kg/hr at idle and 90+ at 3000rpm, engine hot,all loads off.
Also are the oxygen sensor heating circuits functional ?
If you use Testbook for diagnosis you should be able to see how the ecu is set,ie for open or closed loop operation.
 
eightinavee said:
What readings do you get from the maf ? You need 22-25kg/hr at idle and 90+ at 3000rpm, engine hot,all loads off.
Also are the oxygen sensor heating circuits functional ?
If you use Testbook for diagnosis you should be able to see how the ecu is set,ie for open or closed loop operation.
Click to expand...
The only diagnostics I have is Torque phone app and a bluetooth OBD connector so can't get those values.

What's the cost of an effective diagnostics kit?
 
Saint.V8 said:
Without any shadow of doubt...the Blackbox Solutions Nanocom Evolution....
Click to expand...
OK thanks - that looks like £360 odd. Will it allow me to interrogate the ECU and see why there is 'no activity' or no signal from the lambda sensors?

The garage I spoke to suggested that either the ECU was damaged or chipped to remove the Lambda's so (looking at ebay for P38 ECU's) are ECU's plug and play or do they need pairing / programming to the car?
 
The Nanocom will give you a whole raft of information and live data...it will give the lambda readings as Live Data so you can see if they are switching etc...also be able to show you the fuel trims and a whole bunch of other stuff....

As for ECU, they will need to be paired to the vehicle...The Nanocom can do this for you!
 
As an update, this has been annoying me now for a couple of months as I couldn't decide the best way forward having already thrown a pile of cash at the car. The problem was no signal from either O2 sensors.

After much muttering to myself, I thought as Lambda sensors seems to be a relatively common issue I'd find the cheapest ones I could and buy two. Which I did, and had them fitted this morning.

I'm now only getting only one fault (yay) which is No Activity Detected Bank 2 Sensor 1.

Using Torque (I haven't invested in anything else) I see a changing voltage reading from Bank 1 O2 sensor switching constantly between 0.1V and 0.8V, but bank 2 seems constant at about 0.4V, though it did move (and then stay constant) at 0.6V.

From this I'm deducing that the ECU is at least seeing both Lambda sensors, and Bank 1 is operating correctly.

So going forward - does anyone have any useful further diagnostics advice or pearls of wisdom as to where the problem may lie? I wanted to get them fitted so paid a garage - are the plugs straightforward to get to as I'm thinking maybe joint cleaner and some optimistic wiggling of wires?
 
Last edited:
what type of gas system u got.my problem was the fuel trims used a cheap code reader to get the faults eliminated them ( this was after l had done the maf sensor made no difference ) and hey presto 100% running then after letting the gas guy who new as much about gas as l new about gas ovens he fooked it up again so l purchased the cable and software did a auto set on the gas system and now we are running great just keep checking the ecu with a bluetooth adaptor which l leave plugged in all the time and weve had no probs since. occasionaly get a fault weak running on both banks but it doesnt bother it tho hope that helps
 
800jimbo said:
bank 2 seems constant at about 0.4V, though it did move (and then stay constant) at 0.6V.

From this I'm deducing that the ECU is at least seeing both Lambda sensors, and Bank 1 is operating correctly.

So going forward - does anyone have any useful further diagnostics advice or pearls of wisdom as to where the problem may lie? I wanted to get them fitted so paid a garage - are the plugs straightforward to get to as I'm thinking maybe joint cleaner and some optimistic wiggling of wires?
Click to expand...
Yes.

The Motronic ecu will report a fixed value of .5v if it doesn't receive a valid signal from the O2 sensor.



The cheapest way to test is to get the old girl warmed up and get underneath and probe the o2 sensors with a multi meter. You will have 4 wires going to each one - two white for the heater, grey signal ground and black signal. Probe the black one and put the other probe on a good ground. As reported, you should see a swing from 0v to .8v at about 1hz (1second) Im sure the torque app does airflow from the MAF, use the figures 8inavee gave as these are spot on.



If your getting reading from the sensors but not at the ecu a simple continuity test will prove the wiring to the ECU. Lastly have a look a diagnostic software for your LPG system, usually cheap enough and Im going to suggest perhaps the installers have wired into O2 lines - most Lpg software doesn't use this signal but is can be useful for setting the system up so some do use them.


Any more questions feel free to ask, I think I could write a book on this subject the amount of times Ive been through what your experiencing.



Oh, lastly - plug on the ecu. On my P38 corroded pins was giving me wandering signals......
 
bank 1 is on the left hand side of the vehicle sat in the drivers seat looking forward just googled it thought that might have been ur first port of call just done it now have u read the codes using torque then eliminating them worked for me hope this helps
 
also can u tell us what type of lpg system u have some one may b able to point u in the right direction as on my system the petrol learns off the gas system so as in my case if thats not right nothing will b right
 
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