I had a light come up on my dash recently for the transmission, so got the car scanned, with faults relating to the transmission all easy to understand, but also this code

P1138
with a bit of searching it apparently is this: Lack Of HO2S12 Switch - Sensor Indicates Rich

What and where is this sensor and what would be the causes? or is it just a code to ignore?

for those wanting to know this is the site i got my code definitions from Jaguar Check Engine Light DTC Trouble Codes

also the car is a 1995 xjr

 

This refers to oxygen sensors, which are screwed into the exhaust downpipes.

I believe the code is telling you that one of the sensors is giving a fixed reading (too rich, in this case) rather then the desired constant variable reading. P1137 code would be for a fixed lean reading.

The diagnosis chart lists some wiring and connector checks and some continuity tests but, most likely, you'll simply have to replace the offending sensor.

The manual is confusing as to which sensor is likely to be the culprit. In one section the text mentions 'Bank 2 Sensor1' in connection with P1138. Elsewhere it refers simply to 'downstream sensor'. This issue might be complicated because some cars used two oxygen sensors and others used four. Not sure where an Australian market car fits in.

In any case, no, I wouldn't ignore the code outright. At minimum have it cleared and see if it returns

Cheers
DD

 

Thanks for the info Doug, Is that all from a workshop manual? I may have to invest in one if so.

I am assuming this could also be related to what i feel is a higher fuel usage than what i should be getting anywhere between 20 - 25l/100km average, I will definitely have a look at how many o2 sensors there are and either replace all or even just clean them up?

 

Hi MichaelJ,

As usual Doug has covered things well. As he suggests, try clearing the code first to see if it reappears. If not, it may have been due to an intermittent electrical glitch. However, your reduced fuel economy could very well be due to a stuck O2 sensor and over-rich air-fuel mixture. O2 sensors operate at temperatures in the range of 500C to 1000C, so they don't last forever. To my knowledge, you can't clean the sensor itself without ruining it, but you can clean its electrical connector with zero-residue electronic contact cleaner.

You can test the sensors at their electrical connectors with a volt-ohm meter (VOM) to determine which sensor is not swinging between just above 0V and just below 5V. The one that is stuck at or near one voltage is the bad one. The sensors must be at full operating temperature (500C+). Check the service manual for the test procedure and follow the instructions carefully to avoid being burned by the hot engine and exhaust or damaging the O2 sensors. Off the top of my head, I think the X300 O2 sensors have 4 wires, so they are probably not grounded through the exhaust. If you discover they are 3-wire sensors let me know and I'll tell you about cleaning the threads on the sensor and in the exhaust with a battery terminal brush to improve the ground connection.

You can download the X300 Service Manuals, 95, 96, 97 from the "Sticky: X300 'HOW TO' quick links," the second thread from the top at the home page of this X300 forum. There are lots of other goodies there also, such as the Electrical Guide (looks like that links to the Captain Jaguar site, which has been down. If you can't find the Electrical Guide, send me a PM with your email address and I'll send you a pdf copy).

Cheers,

Don

 

Don would it be nice if you can just post it on this site to share will all?

 

You can go to jagrepair.com and download the electrical guides and other useful info

In fact, if the Jaguar Cathouse site is permanently down, perhaps the mods might change the link over to the Jagrepair site?

 

And... the X-300 sensors are titania type rather than zirconium, so they do not actully swing between 1 and 5 volts, but you will instead read much lower voltages, dependent on the input impedence of your meter.

 

when I monitor my 3 (one is dead) O2 sensors with Torque and a bluetooth code reader, it does fluctuate, but I usually see an average 1.3v

 

Hi Cool,

I ony have the Electrical Guide in pdf forum and don't know how to post it to the forum. If you can provide instructions I'll gladly follow through.

Cheers,

Don

 

Hi Ross,

I have a copy of the AJ16 Engine Management System Dealer Training Publication. Page 5-6 (section 5 page 6) describes the O2 sensors and operation.

First, it does confirm your assertion about the type of sensor:

"The heated oxygen sensors are of the Titanium Dioxide type that have a tip composed of an alumina substrate with a thick film titanium oxide element. This type of sensor does not require reference air to detect the oxygen content of the exhaust, so wetting or contamination of the sensor exterior will not affect sensor performance." (So, unlike the O2 sensor on the XJ40, the X300 sensors do not draw reference ambient air through the sensor wiring harness between the strands of copper, which may mean that user installation of the sensor electrical connector on a "universal type" sensor may be less problematic).

Regarding sensor operation, the manual states:

"Air/fuel mixture leaner than 14.7:1 - reference voltage high (maximum 4.89 v)

Air/fuel mixture richer than 14.7:1 - reference voltage low (minimum 0.015 v)

The heater is used to bring the sensor to the active temperature of approximately 500C in approximately 20 seconds after engine start."

(words in bold above are in bold in the manual)

So that leads to a couple of questions:

Is your statement regarding the voltage read by a meter being lower than ~0V-05V due to the impedance characteristics of Titanium Dioxide sensors that leads to an Ohms Law interaction with the meter resulting in a false measurement?

Would a modern digital VOM with an input impedance of, say, 10 megohms be subject to this problem?

Also, due to the frequency of the sensor's alternations between high and low voltages, does the meter read an average of some sort, rather than showing the actual high and low voltages? If so, I assume the actual swings can be seen on an oscilloscope?

Thanks,

Don

 

Don:
You are absolutely right! I had a brain fart and confused the voltage of the zirconium and titanium sensors. The zirconium sensors are a voltage device and range between .1 and .8 or so volts and the titanium sensors are a resistance device and, in the Jaguar circuit, will display the 0 to 5 volt measurement you defined. And yes, if you have a DMM or high impedence VOM, the meter load will be negligible. Many gearheads still use a cheapy analog meter which can have an input impedence low enough to alter the voltage reading. I remember a thread with a fellow who, it turned out, had a $5.00 test meter and could not understand why his measurments weren't right.

It is interesting to notice that the titania circuit yields a voltage that is high for lean, and low for rich. The zirconia sensor is opposite.

 

thanks for all the advice guys, When I get a chance to jumpo under the car I will check it out, not s keen about having to check the sensors when the engine is hot, would a heat gun possibly do the same thing?

 

[QUOTE=MichaelJ.;970069 not s keen about having to check the sensors when the engine is hot, would a heat gun possibly do the same thing?[/QUOTE]

Well, the O2 sensors operate at 500C/932F and higher. Just to put that into perspective, 60/40 solder melts at 188C/370F and the flash point of paper is 350C/662F, so we're talking HOT. I don't think you could get the sensors anywhere near those temps even if the sensor would work properly in fresh air so you could test it (it won't so you can't).

The good news is that the connectors for the O2 sensors are not next to the hot exhaust. The bad news is that they are sandwiched between the cylinder head and bulkhead/firewall. So before attempting to test the sensors, while the engine is cool, it may be helpful to do a little preparatory work along the lines described at this page by Steve, one of the experts at the Jag-Lovers X300 forum:

Go LPG - XJ8 Cruise Control

Others may have some other good suggestions.

Cheers,

Don

 

My suggestion is to acquire a OBD scanner that can chart oxygen sensor levels from the OBD port. It is safer and easier than connecting meters, and nowadays you can be in business for less that $50.00. Google "Torque OBDII software".

 

Don, many thanks

 

I have looked at purchasing one in the past, but my experience is that they are rather average for cars such as the Jag, and in my experience other european cars like the BMW etc, as they often show incorrect or not at all readings unless you pay thousands.

But if this is not the case what brands etc should i look out for?

 

It all depends on what you want to be able to do.

If you want to read and reset performance DTC's (P codes) then these devices are perfectly suitable

If you want to be able to scan, log and graph engine data these also work well.

Most of them work via a wifi or bluetooth adaptor. The best low cost units I've seen are OBD Fusion which is for iPhone or iPad and Torque which works on Android operating systems. I think for the vast majority of people, these will be perfect. I mostly use my Fusion app.

You can spend quite a bit more and buy a dedicated handheld scan tool (I have an Innova 3130) and these work fine but are often more limited in function than the much cheaper Fusion and Torque apps. I have not really seen any difference between the two styles in terms of connectivity or data reading capability.

However if you want to be able to read all the body, ABS and other ancillary codes or be able to run adaptations, program functionality etc. then you will need dealer level software like IDS or WDS from Jag or independent software like autologic.

 

There is a "Sticky"on this, with lots of good advice. The X300 uses ISO 9141 protocol, so make sure that is specified. You are correct that many readers are somewhat problematic connecting.
Remember- there are two parts to an OBDII scanner- the software, and a hardware interface. Many lower enf scanners use an interface called "ELM 327" or its derivatives, and there are now Chinese knockoffs for it. I have had good luck - two knockoffs I set up for friends work as good or better than my "real" ELM module.

A lot of the choice on software (and also which ELM interface you need, bluetooth, usb, etc) has to do with what computer or tablet you want to run. If you have a Android device, you might look at the "Torque" software mentioned early, although it is less fully featured and will (apparently) only chart one parameter at a time, so it is harder to compare two lambda sensor, as an example.

Good luck.

The Chinese knockoff ELM 327 connection modules I have purchased all

 

I've had decent luck with the knockoffs - so far, 3 of 4 have worked great out of the box, but each, after a few months, seems to lose a parameter or two and trigger Torque's "bad adapter" notification. Currently, I'm getting an occasional -40 deg xmsn oil temp (and eng oil temp - cuz xmsn is just eng oil temp with a half-sec lag, or so it appears) I did get one "mini" that would pair to the phone but just sat there like "Tar Baby" thereafter. Amazon took it back. I also have always wondered which, if any of the various blank parameters are due to the cheap adapter not reading vs. maybe just not supported by the 1995 Jag OBDII?

Ross, you can select from among all the various parameters which to log (and at the sampling rate of your choosing) and email those in a .csv file to yourself (couple other formats available, but I forget which) then graph whatever you'd like to see in Excel. Not "real-time" per se, but it does allow you to relax in the comfy chair, air-conditioned room with a cold one as you contemplate what is going on with the engine!

 

Yeah, that sounds reasonable. I use CSV file exports to plot data for fuel trim analysis from my AutoEnginuity and TouchScan programs. Plotting Trims vs. engine load or MAF flow measurement can give some enlightenment, although I still haven't solved my XJR trim issues yet.