1996 Miata Fails OBDII emissions
 

Hello,
I have a 1996 Miata I'm attempting to get to pass the obdII emissions inspection.

Currently it's failing to complete some of the sensor tests:

• Oxygen Sensor - Not Complete
• Oxygen Sensor Heater - Passed
• EGR System - Not Complete
• Catalyst - Not Complete

Everything seems to be functioning normally.
Power is getting to the ECU when the ignition is off.
I have run some drive cycles that are supposed to trigger these tests.

Basically, I've run into a road block.

Has anyone ran across this before?

Thanks,
-Ryan

Hmm, o2 sensors switch at 700+ degrees and at 2400 rpm or so. So you will have to get it completely warmed up and at that rpm to get them to work. The EGR works under a load so basicly half throttle or better on the road generally. If the car has a hard code or in open loop it will go into fixed duty and disregard a lot of inputs.

It would help to know prior history. A typical scenario goes like this. You drive around with the CEL on for a while, knowing an inspection is soon due, so at the last moment you get the needed work done, and the CEL goes off, the ECU has been cleared, so you go for your inspection and despite no evident problems, and hey, you don't pass, with some terse message like "not ready".
This is because the ECU memory latches the faults which existed, and when they are fixed, even though everything is good, and the newly re-initialized ECU dumps the fault history OK, it restarts by putting the car "on probation" (with no indication apparent to the driver) until it has reconstructed a new history database. This means the car has to have been operated over a wide spectrum of conditions for several excursions before the monitoring system decides OK, you've been a good car and can pass inspection based on the background data you need for the unconditional clean bill of health.
Mazda describes these excursions as "drive cycles", and specifies the number of them needed to build the memory database (usually 3 consecutive), but Mazda does not specify exactly what a "drive cycle" is in terms meaningful to the average driver. The thing to bear in mind is that the number of times you use the car is not enough; the car has to be used the requisite number of times over its full normal operating spectrum to ensure you will pass inspection.
So making 10 trips down to the corner store for beer without a CEL on is not going to get you a pass; even 20 trips won't.

Thanks for responding hixx, oldeng,

• Purchased the car a little over a month ago (battery was dead).
• Put the battery on a charger, and it has been fine since.
• Tested for safety and emissions after driving about 50 miles.
• Failed to complete tests, as described, Mechanic recommended driving at least 80 more miles.
• I drove around 400 miles(Highway, backroads, stop and go to work) over 2 weeks.
• Tested again. Same result with codes incomplete.
• Tested ECU power when ignition was off, I have power. (This also probably reset the ECU again, due to unplugging it.)
• Drove around with the OBDII datalogger to record some drive cycles. I met some of the drive cycles I've found elsewhere(not sure how accurate they are).
• My Uncle tested the system with his OBDII scanner (he is a diagnostic mechanic for over 30 years). No issues, no bad sensors, Temperature is fine, everything looks OK to run the tests.

That's about where I'm at now.

Thanks for the tips, I'll try to get some more drive cycles under it's belt.

-Ryan

It's a pretty long shot, but go to http://www.obdii.com/connector.html .Since your Miata is a '96, it might have been in the OBDI/ OBDII compliance grey zone applicable to the same vintage of Proteges; this Autotap site has good material for telling you how to find out if this is the case, and what you can do about it.
You may have to enlist the help of a Mazda shop scan with a hard copy printout to sort this out.

I'm having a similar problem. I took my '96 Miata out of storage a few weeks ago, removed the battery to recharge it, and have driven ~200 miles since reinstalling the battery. I've been to the emissions testing center 8 times and each time they tell me there is not enough history stored.

FWIW, the Air Bag light stays on--is it possible that this fault needs to be cleared before the OBD starts collecting emissions data?

Here is a Mazda drive cycle:

Pre-requisites: MIL off and no DTCs present (this is where clearing your codes comes in); fuel level between 15 and 85%; all accessories OFF; cold start (preferred 8 hour cold soak w/ engine between 68 and 86 deg F at start-up)

1) Start vehicle and idle 5 min.
2) Rev engine in neutral or park to 2300-2700 rpm for 15 seconds
3)Rev engine in neutral or park to 3800-4200 rpm for 15 seconds
4)Idle engine for 20 seconds with cooling fan stopped.
5)Accelerate to 52-55 mph, maintain speed (in high gear) for 1 1/2 minutes
6) Decelerate to 15 mph, and then drive for 13 minutes at speeds ranging from 15 to 35 mph
7) maintain steady 25 mph for 50 seconds.

Each step of the drive cycle indicates a test for a different monitor on the vehicle (catalyst, o2 sensor, evap, etc) so each step is important. Some vehicles are a pain and may require a few drive cycles.