Faulty Lambda reading

[GlennyGills]

Hi,
Having purchased a previously working lambda senior and fitted it, the car passed the MOT ( new cat also needed). I decided to test new sensor with the MX5 Tech diagnostic tool. I get na straight line when warm and running engine around 3600 rpm.

So I am thinking
1. Faulty replacement sensor- but was working when removed from previous car and no error messages
2. Faulty wiring -checked and looks good.
3. Faulty diagnostic tool
4 Faulty ECU - no codes showing.- no error codes displayed.

Is there anyone in Reading/ Wokingham willing to let me test the diagnostic tool on their car?

Thanks

[Mazda Mender]

I'll run the tech reader on mine and see what it should be showing .
M-m

[drumtochty]

Glennygills,

The Gleneagles started production in October 1996.

The factory went over to the 16 bit ecu around August 2015 in the States and I believe in the UK.

In the states a timing disc similar to the MK2 was placed behind the crankshaft pulley to allow the ecu to get an accurate warning of misfires. This in turn in the states allowed the Miata's to be equipped with ODB2 diagnostics for the 1996 model year cars as the 16 bit ECU has more processing power and additional data input lines.

In the UK the 16 bit ECU allowed the cars to have matched keys to prevent car thefts as the keys, immobilisers and ECU were talking to each other. The ODB2 facilities had to wait until the late 2000.

The 16 bit cars from what I can work out had the 4 digit fault codes, the Mx5Tech reader I believe, requires the MK2 cars and the late Mk1 cars to switch to the MK2 settings, perhaps you can advise if this is so with the Gleneagles?

If that is the case, the MK2 cars behave as you advise in that you get a straight line on the MX5Tech reader. The manual with the reader confirms that the MK2 cars do not get a reading from the O2 sensor. If I am correct and it is an assumption, then that suggest a MK1 with a 16 bit ECU may well not provide the readings to the MX5Tech reader.

[GlennyGills]

Wayne, did you manage to test your 1.8 MK1 yet?

[Mazda Mender]

Weekend was a bit of a wash out and last night, I'll get the tester on her tonight.
M-m

[blackyb]

A wash out Buddy. If only!

Our garden is fast becoming like the Sahara desert.

[Mazda Mender]

Whats app vids sent John.
M-m

[GlennyGills]

Video received and thanks - you got a varying line on the O2 sensor, but it was from a 1.8 1993.
Need a volunteer with a 1.8 1996+ MK1 to do a check.

[GlennyGills]

My ECU is a BPU2A which I guess is the older ECU. It still uses the long flash for 10 and short flashes for units. I set it to Mk1 and all other functions works as expected. My concern is that if the Lambda is not being controlled properly then the Cat Convertor will coke up and that is what seems to be happening. BUT during MOTs with a new cat the Lambda reading is within spec. I guess I could ask a garage to give me a lambda reading on a gas analyser.
Thoughts?

[drumtochty]

I have today used my latest spec, MX5Tech reader on a Mid 1996 registered MK1. It did the straight line readout of the O2 sensor voltage both setting the car as a MK1 and as a MK2.

Therefore, I assume the 16 bit ECU as advised in the MK2 section of the reader user manual also applies to late Mk1's. I.E. no useful voltage readout of the 02 sensor on the 16 bit ECU MK1's

[GlennyGills]

Many thanks for that info. It gives me some piece of mind.

[drumtochty]

I can confirm that the BPU2A ECU is the first version of the 16bit ecu fitted to the Mark 1 manual cars from mid 1995 through 1996.

[GlennyGills]

Hi I contacted Ian from MX5 Tech and got the following response:

Hi John,
The oxygen sensor doesn’t operate until normal operating conditions have been reached. This can take a few minutes. However, it sounds like you’ve let the engine get warm and kept the revs over 3500, so you should normally see the line going up and down.
Usually the only reason you won’t see this is if the engine isn’t warm enough or the O2 sensor isn’t working!
Regards
Ian

So is the new sensor bad or is the wiring bad. Any ideas on how to check?

John

[drumtochty]

You only see the data if it comes from the ECU to the data port on the nearside wing. I had a 1996 UK spec car at full temperature and got no reading on the MX5Tech tool re the O2 sensor. The car had recently passed an MOT with no issues at all regarding emissions.

If the O2 sensor was faulty as you are worried about it would not pass an MOT.

Like your car it had the 16bit ecu.

Mazda dealers had a different code reader for the 16 bit cars as the original code reader only gave full info from the 8 bit ECU cars.

Therefore if you are still concerned why not ask the MX5Tech why Mazda dealers had to use a different code reader for the 16 bit cars?

The info is not available from the same pins on the diagnostic socket. If I have time I will look to see if I can find out any more info.

[GlennyGills]

Hi,
My problem was that since changing the original Mazda cat several years ago I went through "cheap"cats every year. I have now got a new "expensive" cat and new O2 sensor, so I wanted assurance I wasn't coking up the cat. Lambda reading was fine on recent MOT.
What you are saying makes sense and thanks.

John