2008 Mazda 3 - 2.0L Standard Trans Ignition problem

We tested the battery - to pin 1 when key is in crank and the light illuminated.
When testing the battery + to pin 2 the light did not illuminate at all.

Correction on the ground test, we testing it incorrectly. We got 0V in both cases.

And I was incorrect in the dash lights going out when starting, it is only the display on the dashboard that says Hello that goes dark when attempting to start.

jonkirkross wrote: We tested the battery - to pin 1 when key is in crank and the light illuminated.
When testing the battery + to pin 2 the light did not illuminate at all.

Gotcha, thanks for the clarification! The ignition switch is working. Now we're going towards the shift interlock or the PCM.

Find the clutch switch under the dash and probe both wires with the test light connected to B+, pedal depressed and key in crank. If the switch is good, both wires will illuminate. If it isn't, only one will illuminate. If the PCM isn't proving a ground, neither will illuminate.

We tested and neither is illuminating with the key in crank position.

I also tested ohms and it was infinite resistance when not depressed and showed a closed circuit when closed.

So, the conclusion is that the circuit is good.

What does this conclude? There is an issue with the computer?

Yep, the PCM is not providing the ground for the control side of the relay. The rest of that circuit is good.

Now we go towards the PCM and it's powers/grounds/inputs. I don't remember if you said or not - does the check engine light come on with the key on? That'd be a big clue to an inoperative PCM.

Another quick check would be looking for 5V at one of the engine sensors. The camshaft position sensor would be my first choice, being out there in the open and accessible. Disconnect it and check all three wires for voltage with your multimeter, KOEO. At least one should have 5V.

We did test the MAF sensors and found a 5V on that previously. Does that conclude a good PCM?

Sweet, way ahead of me. It doesn't tell us the PCM is 100% good, but it's at least powered up and talking. Do you have a scanner or code reader, to check communication? While we're on the subject, do you see any kind of anti-theft light on the dash with the key on? Does it come on and go off, or stay lit?

I did some more digging in the wiring diagrams, and found this on the 2008 MY:



This shows two more switches associated with the manual trans option. Neither is the clutch interlock switch we tested earlier - that one is further up on the same diagram. If the anti-theft light come on and goes out, then I'd be tempted to pursue these switches.

The anti-theft light comes on and then goes off.

Connected to the obd2 via elm127 to ODB Fusion. There is a code of an O2 sensor P0138.

Also, it does not pull freeze frame data, I'm assuming that's because it's not running.

Where do I find the other two sensors? The neutral position switch and the clutch pedal position switch?

Thanks for all of your assistance today, I hope we find the issue soon!

jonkirkross wrote: The anti-theft light comes on and then goes off.

Super glad to hear this! :silly: I REALLY didn't wanna go down the anti-theft path.

Connected to the obd2 via elm127 to ODB Fusion. There is a code of an O2 sensor P0138.

Also, it does not pull freeze frame data, I'm assuming that's because it's not running.

Also glad to hear this.

Where do I find the other two sensors? The neutral position switch and the clutch pedal position switch?

I wish I knew! :silly: I gotta do some more research on those. I'm honestly not even sure they'll cause a no crank condition. But, I gotta figure the PCM is watching them for some reason...

Thanks for all of your assistance today, I hope we find the issue soon!

Thank YOU! I know this process isn't straightforward, so I appreciate you staying with me.

Is the PCM still accessible? I'm tempted to suggest going there next.

Rather than digging around for the Neutral Switch and the Clutch Pedal Position Switch, I figure it's easier to find the signal wires at the PCM connector and check their operation that way.

Unfortunately, the OE diagrams don't point out pin locations, or have all the PCM pins in numerical order so we could figure out color sequencing. You're looking for a black/orange wire for the Neutral Switch, and a black/yelllow wire for the Clutch Pedal Position Switch. I know, that doesn't narrow it down much. :silly: I can definitely say they're in the same PCM connector (of the two).

They're both going to be pull down switches, so we're looking for 5V or 12V with the switches open, and 0V with them closed. You may have to work the shifter to make the Neutral Switch work. If both change states while working the clutch or shifter, then I'm gonna figure they're working correctly.

Am I ever glad the immobilizer is out of the picture, Hope these pics help.

THANK YOU. :woohoo: I was giving myself a headache trying to decypher Mazda's goofy pin numbering system.

Noah was also nice enough to hook me up with an alternative diagram. I'll post it up when I get a chance.

Im trying to dig up the inputs Jon needs to start this thing lol!

Less detailed, but way more convenient than surfing through the OE diagram. :lol:

Tyler wrote: Is the PCM still accessible? I'm tempted to suggest going there next.

Rather than digging around for the Neutral Switch and the Clutch Pedal Position Switch, I figure it's easier to find the signal wires at the PCM connector and check their operation that way.

Unfortunately, the OE diagrams don't point out pin locations, or have all the PCM pins in numerical order so we could figure out color sequencing. You're looking for a black/orange wire for the Neutral Switch, and a black/yelllow wire for the Clutch Pedal Position Switch. I know, that doesn't narrow it down much. :silly: I can definitely say they're in the same PCM connector (of the two).

They're both going to be pull down switches, so we're looking for 5V or 12V with the switches open, and 0V with them closed. You may have to work the shifter to make the Neutral Switch work. If both change states while working the clutch or shifter, then I'm gonna figure they're working correctly.

Sorry for taking so long to get back to you, I was away at a tradeshow for work and then my wife and I took a weekend vacation to Niagara on the Lake and then I was busy with work and finally got to test out these latest suggestions.

So, we tested the Neutral Switch and the Clutch Switch against B+ and received a reading of 12V for both in both open and closed, i.e. when cranking and not.

I was wondering, because the car was in a collision, could the problem be a positive short off of the alternator? If so, how could we test for this?

Thanks again for all of your knowledge and assistance!
Jon

No worries about the delay!

So, we tested the Neutral Switch and the Clutch Switch against B+ and received a reading of 12V for both in both open and closed, i.e. when cranking and not.

Sorry, but I'm not quite sure I understand these results? Was this done with a DMM or test light? If you wouldn't mind, try a DMM with the ground connected to B-, probing the neutral switch and clutch switch. KOEO, work the shifter and clutch without cranking, and tell me what you see.

I'm thinking that the neutral switch isn't going to be a cranking input, but the clutch switch might be. If you see 12V on the clutch switch circuit with the clutch pedal all the way down, then I'd suggest a bypass test. Connect a test light to B- and probe the clutch switch pin, then try cranking again. Use the DMM to confirm 0V on that circuit if needed. If it now cranks, we're on the right track. If not, we'll need to go in another direction.

Sorry that I went away for a while again. Winter hit and I had to clean out my garage to move the car in.

I tested the Clutch with a DMM and was getting mV with the clutch engaged and disengaged.
The Neutral test gave me 12V when in gear and mV when out of gear.

Does this mean that the clutch sensor is the issue?

No worries, sorry for taking awhile to get back to you! :blush:

So the neutral switch works, but the clutch switch would seem to be stuck closed or shorted to ground. There's definitely no switching going on there.

Would you mind testing that same clutch switch pin at the PCM with a test light? Light connected to B+, see if the bulb lights. That'll confirm a stuck switch or short to ground.

If the bulb lights, then you've got a couple options. My first suggestion would be to cut the black/yellow wire for the clutch switch somewhere close to the PCM, but easily repairable. Then, either try to crank the engine, or measure voltage on the PCM side of the cut. Should be 12-ish volts. If the engine now cranks, we're onto something.

The other option would be to track down this clutch switch and do more testing there. I have no resources to tell me where this switch lives, exactly. Have a closer look around the clutch pedal for any switches that might be hiding.

So I couldn't get the trouble light to work on the B+ to 1D (clutch switch), so I tried cutting the wire anyway. Then I re-tested B- to the clutch switch KOEO and I got 11.8 V on the DMM when the clutch was not engaged and random mV when engaged. So this is not the issue....

What should we check next?

I tried jumping the clutch position sensor. The light comes on with the key off between B- and 1D. Then when the key is on the light goes off whether the clutch position sensor is bridged or not. Also, the engine does not crank whether 1D is cut or not... is this a short or what could it be?