Engine Light Stays On.

[5isalive]

Hi all,

For the past few months the engine light in the dash of my NB would come on periodically, but if I turned the car off and then restarted it, the light would go out.

Obviously I thought that the oil was low or the coolant may need topping up, but this hasn't been the case at any time.

Now, as of a few days ago, the light stays on all of the time. Please, can someone give me an idea as to what may be causing this?

Thanks for your time.

Wayne.

[ManiacLachy]

You need to find out what the error it's trying to tell you is. It could be many things and we can't say from just the light. You need to get your hands on an OBD2 scanner and investigate.

You can get bluetooth ones these days that talk to an app on your phone, or a dedicated plug in scanner. Otherwise, visit a workshop and ask them to pull the code for you.

The code is only the start though, sometimes it's not as simple as low oil/coolant, and the error message is merely indicative of an error further upstream. But it gives you and us a clue

[greenMachine]

What ML said.

Is the car running ok, any flat spots, hesitations etc? Fuel consumption not abnormally high (or low )?

It may just be a dud sensor, or something equally simple and easy to fix, but you don't know until you know. You especially do not want it to do anything that might result in big bills, like running lean, sudden loss of power/cutting out. If it's not your daily, I'd limit my use as far as practical, just to be on the safe side.

[93_Clubman]

Few initial checks you can do:
ensure fuel cap if on tight;
ensure no water in spark plug wells;
check all fuses (both under dash & in engine bay); &
ensure fuel cap seal is sealing.
Continuously lit engine light is usually emissions related, while flashing engine light is more serious. Disconnecting the battery will clear the error code/s stored in the ECU, & initially at least make the engine light go out.

[5isalive]

Thanks for the replies so far.
Unfortunately, I'm not very mechanically minded, so I'll go and find someone that can do a scan and see what that picks up.
I thought it must be something as simple as a sensor, but it seems maybe not.
Anyhow, I'll get back to this post with any results that are found.
Once again, thank you all for your valuable input.
Cheers, Wayne.

[5isalive]

Hi all,

I had my mechanic do a scan today and it came back with the following two possibilities.

From the top of the diagnostic it says...

Diagnostic Path: Manually Select > Vehicle Select = MX-5 > Capacity = 1.8L > Engine Type = BP > Model Year = 2000 MY > Transmission = Manual > Health Reports

I'm a little confused with the "Model Year" section as mine is a 2003 model. Is this an error from the mechanic or is it a standard read out?

POO12: Camshaft Position Timing - Over-Retarded (Bank 1). PCM (Powertrain Control Module)
POO31: HO2S11 Circuit out of range low voltage. PCM (Powertrain Control Module)

I'm hoping someone here may have some idea as to what this all means.

Thanks again for any help.

Cheers, Wayne.

[bartmanftw]

The selected model or model year doesn't matter when reading OBD diagnostic trouble codes (DTC). You will still get the same DTC values.
It's only useful for decoding manufacturer specific codes and the two you have are standard emission required codes.

Did your mechanic tell you if these codes were active or in history?
P0012 is to do with the VVT system. Over-retarded means the actuator isn't moving so I'd start by checking the circuit to the VVT solenoid.
P0031 is O2 sensor. It probably just needs to be replaced.

[ManiacLachy]

It's times like this we need a "pos-cat" system like MiataTurbo, that is such an excellent and helpful answer, bartman!

[greenMachine]

It's times like this we need a "pos-cat" system like MiataTurbo, that is such an excellent and helpful answer, bartman!

+1

Many the time I have instinctively looked for that, only to realise I am not on that board.

[5isalive]

Thanks for that Bartman.
No, the mechanic didn't say whether it was history or active. I'll ask him today.
As for the O2 sensor. Is that something that can be replaced easily by a laman like myself?
Where would it be located?
And the "VVT System". What is it and what does "VVT" signify?
Are these costly parts and are they difficult to replace?
Sorry for all the questions, I'm a musician, not a mechanical bone in my body, so 90% of this stuff goes way over my head.
Thanks again for your assistance.
Wayne.

[bartmanftw]

If you purchase a new o2 sensor specific for the mx5 with the correct connector and wire length then it's pretty simple to change over. Just unplug the older sensor (4-way connector located on the rear right of the valve cover) and remove from the exhaust, then replace with the new one. You will need to jack up the vehicle to get to it and will also need a 22mm spanner or o2 sensor socket.

VVT is variable valve timing. On the NB8B engines the intake cam has a variable cam gear that's actuated using oil pressure. On the top of the valve cover there's a solenoid with a 2 pin connector that controls the oil pressure to the actuator. Inspect the connector and make sure it looks ok and then test if it has 12V on one of the pins when the ignition is on. Unfortunately testing the control circuit isn't as simple as you would need to check the signal using an oscilloscope.

A cam sensor fault may also trigger the P0012 and not set the cam DTC, but usually cam faults cause misfires and stop the engine from running.

[bruce]

As you say you are not mechanically minded, leave it to the mechanic.

[5isalive]

Thanks so much Bartman. I very much appreciate all the help you've passed on to me.
I think I have to agree with Bruce though. It might be better to let the mechanic tackle it.
I'm hoping one of either of these fixes solves the problem.
Thanks again.