Oxygen sensor

[NCB ELAN 1991]

This is my first post and I hope not to upset anyone by asking a question that has already been answered:
I have just acquired a 1991 Elan SE with 100830 km.
The car has been off the road for over 2 years (the previous owner died) and I want to present it for the MOT - TÜV here in Germany. This is a 1 owner car which has had all services carried out by the local dealer. The executors of the estate could not find the service history but I knew the owner and the car since 1991. In fact it had been serviced only 3 weeks (85 km) before being parked up.

The CEL is not on but Fault Code 13 is stored. I have an original Lotus Tech 1 tester and the only readings which are out (after the fans have switched on and off 3 times) are OXYGEN SENSOR which remains constant around 457 instead of varying between 50 and 950, and, OPEN/CLOSED LOOP which naturally remains OPEN.
I have searched the forums but did not find any answers. Perhaps someone has had the same problem.

Thank you in advance.

[Simon_P]

Disconnect the battery to clear the code.

Have you found the closed loop manual in the manuals section? and the wiki?

[NCB ELAN 1991]

Simon,
Thank you for your prompt reply.
I had to replace the battery which, after 2 years, was dead. I will disconnect it and see if the fault code disappears.
Yes, I do have the manual and will have the oxygen sensor circuit checked out. The fact that I have a reading for the sensor suggests that it works but perhaps the heating circuit is faulty.

[NCB ELAN 1991]

I should have added that I did clear the code using Tech 1 but I will try disconnecting the battery.

[Fredjohn]

I note you have a 91 SE. The SE model did not have a factory fitted oxygen sensor. Only the S2 had one for emissions reasons.

However the previous owner may have fitted it along with the correct ECU chip.

To check: you can see the sensor and its wire to the left of the turbo. Also look at your Tech reader, it may tell you the chip. 9929 or 9930 are SE no sensor, 1499 S2 with sensor.

I suspect that as the O² reading is constant and it is saying OPEN, you have an SE with no sensor fitted.
Hope this helps.

[chrism]

NCB ELAN 1991I haven't any experience of a Lotus Tech 1 tester but it may be set up to test for an m100 O2 sensor and might be responding by default to your lack of sensor if it isn't there(?)

An easy check:- If you can confirm that you've got one of these

then your O2 heater circuit may be broken* in some way.

I gather an O2-sensored SE 'works off' the alternator charging circuit, so I'd be interested to see if your alternator warning light stays 'on', in which case the heater circuit won't be working properly. If works as normal I think I'd substitute or replace the O2 sensor and its lead.

*It could also be that an O2 sensor has been retro-fitted but I've found that there were many SEs (my own '90 SE included) that had most, but not all, of the wiring in place and this might not have been fully realised at the time; it's only obvious 'when it doesn't go'... In my case after completing the wiring loom I felt I needed to further verify - by using elanscan - that mine had started cycling after conversion to closed loop.

So, I found that it can be a bit of a minefield...(Also I found the wiki instructions were a bit confusing...)

Also I'm not completely sure that closed loop is dependant on fan-tripping engine warmth - let alone 3 cycles of it? Most of the time my own fan doesn't even come on, yet I've been closed-looping around...

[dapinky]

To try and clarify some of the above advise (which is correct, but may lead to confusion as it isn't complete!)...

..... but first, a disclaimer - I've never even seen a Tech 1 tool, let alone used one..... I know it is "similar" to elanscan, but i can't make any comment on it's calibration, use and results.

When John says only the S2 has the 1499 chip, that isn't entirely true - the first-gen turbo cars intended for Europe, USA and ROW all had them - and (obviously) Lotus will have trialed them for whatever market was intended, and then done the simplest thing to get the car to comply.....so generally, early UK cars have a 9929 Prom, later ones have a 9930 Prom, EU/FED/ROW cars have a 1499, and those intended for California market have a special box of unicorn dust which is known to absorb anything at all harmful to the environment........

Really, it would have been so much simpler if they all had the 1499, and then a Cat was added where required - but it didn't happen.

Anyway, basically, many of us have retro-fitted an O2 sensor and a 1499 Prom to get cleaner running, better economy and whatever other benefits we feel we get. As Chris says, not every car has the complete wiring for the ECU to recognise the sensor (but 90% do) and it is easy enough to add 2 lengths of wire between the ECU and the engine bay loom if you don't.

Elanscan will tell you if it is collecting a signal from the O2 sensor - but I don't know if Tech 1 will?????

As for running through 3 fan cycles, whilst it seems OTT I can see the logic (as well as accepting that it may just tell you to do it in the instructions on Tech 1) - a 'closed loop' system will only work above a certain temperature - which is why the elan uses a heated sensor. When you first start the car, whatever chip is fitted, it will be running 'open loop' until it gets to the right temperature (before you ask, I don't know what the numbers and/or timings are for this to happen, sorry!)

Also, if it ever falls into 'limp-home' mode it will be 'open loop' as all but the very basic sensors are disabled at that time.

I'm not trying to be nit-picking or argumentative against the other posters, as what they say may well be helpful - but I wouldn't want you to rule out possible causes and effects based on incomplete information, believing that it couldn't possibly apply.

Just for your information, the Os sensor is a Bosch 15701.... I just paid £29 for one from Rockauto.com.

[chrism]

Oh...I paid ~£65 for my O2 sensor from one of our UK (s)dealers...(yeah...I know - stoopid price - but, to my defence, it was before your excellent thread in Part Cross-Reference)

And ooh...my '90 m100 was one of the unfortunate 10% SE-ers w/out complete wiring...

Sympathy please, BUT to add to dapinky's 'right temperature' comment I've just looked at my last elanscan and I can confirm that my 1499 SE goes 'closed loop' at the same time that the thermostat opens ,~82C, roughly 220 secs after start-up; my CO potentiometer/Oxygen sensor starts it's usual fluctuation between a bit above 0 and a bit below 4V. O2 sensor oscillations, too, on whatever scale that is.

So...I'm wondering if the alternator light is the prime instigator of the process by providing the heating current/circuit as it goes out, or whether the process continues separately or is supported via the coolant sensor - which is why I'm anxious to learn about the NCB ELAN 1991 alternator light

[Fredjohn]

Chris
If you look at the wiring diagram you will see that the CEL and O² feed are in parallel not in series.

So they are not interdependent.

Also the CO potentiometer is 'disabled' when you are using closed loop with O² sensor. So elanscan won't read it or will return 0. (I think!)

[chrism]

Thanks FJ.

Erm...I meant red alternator light that goes out when we start up and flashes if we aren't ticking over fast enough. Is that connected in any way to the O2 feed? I gathered that it provides a heater circuit/current when it goes out as the engine fires up. If there's a parallel connection does that mean that as the red light dims the current diverts to the heater circuit, I wonder?

Also, yes I agree the 1499 map should denature the CO pot input (situated near the ecu) - but my EScan gives me a couple of 'O2 sensor graphs' vs Time(s) (picced)

This is 'CO potentiometer/Oxygen sensor':



and this is 'Oxygen sensor (integrated)':



This is the coolant temp graph for comparison with 'closed loop' opening: (admittedly scale could be better...)


As you can see they're all from the 1499 map data...

ps I'm just noticing that the 'closed loop' start up seems to occur even before the 'stat opens...
pps the last bit of the graph is where I started up and moved the car into the garage half an hour later or so

[NCB ELAN 1991]

Firstly, let me thank everyone who has offered advice with this issue. I am overwhelmed by the response.

@Fredjohn – the oxygen sensor is a factory fit. All SE models built for the German market were fitted with the sensor. The PROM ID is 1499.

@chrism – the alternator light does not display any unusual behaviour. It goes out as soon as the engine starts.

@dapinky – the 3 fan cycles may be misleading. When I trained on Esprit and Excel in 1988 we were taught to wait for the fans to cycle 3 times before attempting to set up the carbs. This may no longer apply to fuel injected engines but old habits die hard. I am also certain that the running temperature has been reached.

Tech 1 is the tester that Lotus introduced for diagnosing faults on ’88 MY X180 Esprit with MPFI fuel injection and also for M100 Elan. I will upload some photos showing it in use. The ElanScan graphs look very impressive but they baffle me.
I know this car since it was new and know that it always displayed CLOSED LOOP, even 3 weeks before being parked up for over 2 years. I still hope that it is just a bad contact somewhere. The interior was covered in mildew and even the engine bay was wet when I collected the car.
The EMJ section (Closed Loop Elan Turbo with Catalyst) of the Service Notes recommends checking the sensor circuit. Because prodding about in wiring looms and ECU connectors is not my strong point I must leave that to an expert.
I will keep you updated.

[chrism]

Hi again NCB ELAN 1991.

Yep, new to the forum a year ago I've found that LEC always has a refreshing response. Most problems have been wrangled by someone and the old-timers are very tolerant when us 'newbies, late to the party' pick up on those issues that were 'done + dusted' ages ago.

I agree, those EScan graphs (and, indeed, many aspects of EScan) are confusing. To me they both just mean that the fuelling is being 'managed' and (now) continually optimised by 1499 ecu. I included them to add meat to the bones of dapinky's closed loop <-> temp thoughts. From their data 'closed loop' seems to cut in surprisingly quickly - and definitely no need for your fan recycling, it seems. Interesting tech, but I think you may be in a minority with your Lotus Tech 1 tool...

I'm glad your promid value is 'sorted'; I get the impression that it's time to renew that O2 sensor, then. Dapinky's RockAuto recommendation is one I wish I'd known about earlier.

Loadsa luck + keep us posted

[Fredjohn]

Glad we sorted out your O² sensor existence! I hadn't realised D SEs had the sensor.

Judging from your most recent post, my guess is that either you need a new sensor or there is a break in one of the wires to the sensor.
The heater wire is easy to check: remove plug from sensor, switch on and run a multimeter to earth. Should read 12v.
The signal wire may be more difficult. Continuity check between plug and the plug into the ECU should do it. Hopefully the ECU is OK!
See wiring diagram to help.
See dapinky's post for new sensor source.
Good luck

[Simon_P]

I think recall that the closed loop requires several conditions to be met and I think temp>50C is one of them.

As Fredjohn says the O2 sensor check is a straightforward check suitable for complete amateurs, I don't think you can break anything so have a go!

[chrism]

Yes, Simon_P. If we superimpose the O2 sensor/Coolant temp graphs previously posted it'd support your figure and show a switching point of between around 50 - 60C after roughly 100s. Certainly before the 'stat fully opens.

(It would be easier to compare if we could overlay these graphs for greater accuracy in the same way that we can overlay separate EScan maps/files ...)

[NCB ELAN 1991]

Happy Days,

the Elan just needed to stretch it's legs on the open Road. Oxygen sensor ok. TÜV / MOT done and dusted. The only thing we have to take care of is the LH rear brake pressure
- possibly caused by lack of use.
I have attached some photos of Tech 1 in use. It reads 34 parameters and allows us to switch solenoids etc. on and off.
Once again many thanks for your support. I'm sure I will be contacting you again in the future.

[chrism]

That's good news - and we've learned a lot from your post.