[Guest]

I have a 93 mx6. My problem is that while I'm driving my car the check engine light tends to turn on. This may not sound odd but it is, you see, the only time the light comes on is when I drive over those relectors that divide the lanes on the freeway or when drive over a sudden dip in the road. When the check engine light is activated the engine stalls for a split second, performance is not affected with the light on with the exception of the sudden stall. Does any one have any ideas...I have checked the computer codes that showed a bad crankshaft positioning sensor, which I replaced and then erased, but the same code continues to show up. Any information will be appriciated...mazdart.

 

[Mike 94PGT]

Was it NE2?

Which code did you pull out of the PCM? There are two crank position sensors on a '93: one down by the crank and one in the distributor. The one down by the crank is the "primary" sensor so I'll assume that you got a code 2 and replaced that sensor.

It sounds like you've got a bad connection. When you hit the dip in the road or those "cat's eyes", the vibration might be enough to cause the contact to become momentary, causing the PCM to lose the NE2 signal. When this happens, the PCM won't fire the injectors or signal the distributor. It takes 3 pulses (IIRC) of the 'G' sensor (cam position sensor in the disty) with no NE2 pulses before the PCM flags an "NE2 missing" error (code 2) and switches to the backup CKP sensor, NE1. You sense this delay as the engine dying momentarily.

Open the hood and locate the NE2 sensor connector up by the coolant system cap near the accessory side of the engine. With the engine running, tap the connector with the handle of a screwdriver. Try moving the wires around a bit. Look for the engine to stumble and/or the CEL to come on. I suspect the PCM-side of the connector may have a bad crimp joint, corrosion etc causing momentary connections.

If nothing happens, you may have to move your search inside the car down by the PCM.

 

[Guest]

already checked, but will check again!

Hey Mike, thanks for the info...but even prior to changing the primary sensor by the crankshaft I checked all the connectors for problems...maybe it was an oversight...I will check it again. You do have a valid point however because after the check engine light is activated the car runs just fine... You are saying that when the PCM switches to the secondary it stays at the secondary until the car is turned off, right? Is the informatiom that you are providing from a personal experience or from litiature that you have read. Well thanks again...and if you have any other info on the subject please write. Art

 

[Mike 94PGT]

Re: already checked...

Hey Mike, thanks for the info...but even prior to changing the primary sensor by the crankshaft I checked all the connectors for problems...maybe it was an oversight...I will check it again. You do have a valid point however because after the check engine light is activated the car runs just fine... You are saying that when the PCM switches to the secondary it stays at the secondary until the car is turned off, right?

The PCM will continue to use the backup sensor as long as the primary sensor is not functioning. If the CEL goes out, the PCM is then using the primary again.

Is the informatiom that you are providing from a personal experience or from litiature that you have read. Well thanks again...and if you have any other info on the subject please write. Art

Alot of each: I have shop manuals for the 94MX6 and 93PGT as well as extensive experience reverse-engineering the engine control system (PCM code, hardware, sensors etc.) See my web site under "PCME" for details on some of the stuff I've done.