Help with 99 Miata check engine codes

CEL came on and I pulled three codes:

p0106 - map sensor

p0420 - catalyst efficiency 

p0442 - evap Small leak

last year, I got the p0106 code, reset it and didn’t see it again til now.

My my questions are:

Could a bad/intermittent map sensor cause the p0420 code?

does anyone know what this o2 sensor data means ?  To me it looks like the pcm has the sensor 1 heater on and the sensor 2 heater turned off.  My scan tool doesn’t seem to show live data from either o2 sensor.  Was trying to verify both sensors were working.

I did reset the codes after checking the vacuum lines to the map and solenoid. Have not come back after about 80 miles. 

Thanks

Your codes wont reset until you go through all of the readiness states.

"

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. 

To answer your question, no, the MAP sensor wont trigger a catalyst efficiency fault.  The MAP sensor is used just for EGR- to measure how much is flowing, the primary air flow measurement is MAF.  

Given this is almost a 20 year old car, it's pretty likely that your catalyst is just done.

The O2 info is what you think- the front heater is on, the rear heater is not.  How soon after a start did you do this?  For a car of that vintage, it's likely that the rear sensor heater isn't turned on for at least a min, whereas the front one will be on within the first 20 seconds.  If there was a specific sensor fault, it would have lit the light.

Thanks for the info. 

Im not sure how long the car was running when I checked o2 sensor but it was less than five minutes. Probably one or two. 

I did check obd readiness after 60 miles, and everything was complete with no codes except evap test was incomplete. So, the map and catalyst codes seem to be intermittent. I am trying to diagnose vs throwing parts at it. 

Heaters for both sensors come on with ignition since they are on the same circuit. Either the wires or the O2 sensor at position 2 are defective.

ChasH said:

Heaters for both sensors come on with ignition since they are on the same circuit. Either the wires or the O2 sensor at position 2 are defective.

Are you sure about that?  OBD needs to detect issues separately- so I don't think the circuits are the same.  Also, they very much don't turn on at key on- as the sensors wait until the risk of water drops go away so that the heaters are not cracked.  And that time is very different for the main O2 sensor and the one downstream of the catalyst(s).

If the sensors are actually defective, the OBDII requirement is that it's detected and listed as a fault- which it isn't being done.

alfadriver said:

ChasH said:

Heaters for both sensors come on with ignition since they are on the same circuit. Either the wires or the O2 sensor at position 2 are defective.

Are you sure about that?  OBD needs to detect issues separately- so I don't think the circuits are the same.  Also, they very much don't turn on at key on- as the sensors wait until the risk of water drops go away so that the heaters are not cracked.  And that time is very different for the main O2 sensor and the one downstream of the catalyst(s).

If the sensors are actually defective, the OBDII requirement is that it's detected and listed as a fault- which it isn't being done.

I have not personally verified it; but this is what the schematic suggests. The heaters are common- the voltage circuits are indeed separate.

Please consult a schematic.

In reply to ChasH :

I'll stick with my experience.  Knowing OBD, and how O2 sensors are heated, it's highly unlikely that they run the same heater circuit. 

They may have the same voltage source, but the grounds are supplied by the module, which is how the system is controlled.  Each heater has to be detected by it's individual failure, not as a pair.

Ok. So around 100 miles since I reset codes.  No CEL, but evap test still incomplete. 

I did find another screen on my code reader and got live o2 data. Sensor1 bouncing between .08 and .9 volts roughly. Sensor 2 staying under .12v. Does this indicate cat is marginal?

Oh and both o2 heaters showed “on” for this round.

sensor 2:

Unfortunately, resurrecting this thread - no real progress made.

I still am getting the P0106 - MAP sensor code.  Things I have done so far:  Checked operation of MAP solenoid.  Cleaned connectors and verified 5V at wiring connector for solenoid and MAP sensor.  Replaced MAP sensor with new, OEM part.  checked all hoses - replaced one on the solenoid that seemed to fit slightly loose.  Replaced PCV valve and rubber grommet since the grommet was hardened and the fit to PCV seemed slightly loose.  Cleaned intake manifold ports (none were clogged).

P0106 code comes on intermittently - the CEL will turn off for a while and then come back.  This has been occurring for over a year - car is not a daily driver.

There is also an EVAP code happening that is new to the past 3-4 months - either small or large EVAP leak (have seen both).  replaced gas cap - no change.  My understanding is that this should be unrelated to the MAP code.

Advice on where to go from here?  Could the EGR valve be the problem?

In reply to sevenracer :

Yes, it can be the EGR system.  The MAP sensor is only used for EGR, anyway.

Before cleaning out the EGR system, one other thing to try (if you have no done it already) is to move the MAP sensor to the outlet under the throttle body.  I did that many years ago, and it fixed that, and kept the EGR code (one more thing I need to restore on my car).

I would change all the vacuum hoses including the EVAP related ones. 

I chased a code for months and the culprit ended up being a vacuum hose that looked and felt ok but must have been leaking because the problem went away when I changed it.