Crankshaft Position Sensor - Testing?
 

1996 4Runner SR5 2WD 3.4L 5VZ-FE V6 A340E, 280K miles...

I've got a weird timing issue, with a P0505 code. I've checked the IAC valve per the procedures (resistance in spec, cleaned it all out, operates open and close with 12V). Air assist checks out per the procedures (drops to just under 500RPM when air assist hose is plugged). I have no vacuum leaks. MAF seems fine. Idles normally at operating temp (about 700RPM), idles low at cold start (see below).

Symptoms when cold: idles up to about 1200RPM at start, then immediately (within 2-3 seconds) settles around 700RPM. Per Torque app, timing advance is about 5-10 degrees positive (I presume that means before TDC). When I push the accelerator, it revs up fine to about 1300RPM, then suddenly begins to stumble... when that happens, timing immediately jumps to about 15-20 degrees negative (I presume that means after TDC). If I continue applying throttle, once it reaches about 2200RPM, timing jumps back to normal and then RPMS really shoot up fast (due to accelerator pedal being pushed down pretty good)

Symptoms at operating temp: In park/neutral, revs up normally no issues. Under load, i.e. in drive, even the slightest acceleration causes stumbling (and the drop in timing). At normal driving speed, easing slightly off the accelerator causes the stumbling. Gentle/normal acceleration causes stumbling, but if I accelerate a little aggressively, timing evens out and seems to run right.

I pulled the crankshaft position sensor out to check it, and I checked resistance with a multi-meter. It was also a little dirty, so I cleaned it off with a rag. Shows 0 resistance (i.e. no circuit) on the bench, but it does show varying resistance when I run a magnet by it. I don't have a scope to check what (if any) voltage it's putting out.

The reason I'm looking at the crank sensor is I've replaced the wires, coil boots, throttle position sensor, fuel pump, fuel filter, the plugs are relatively new (dual electrode NGKs)... so I've pretty much ruled out the fuel/air (I think), even though the only code I'm getting is P0505. The intake air temp and engine coolant temp both read right on my Torque app.

If I understand correctly, the engine timing (i.e. the crank sensor) is part of the idle air control system calculation. So.... is the crank sensor in the 5VZ-FE supposed to have no resistance until the magnet runs by it? I haven't swapped out the ECU, but that's kind of a last resort given the cost and that ECUs are typically the last thing to rule out.

Any advice is welcome! Thank you!

The resistance is not correct.
Per FSM resistance when cold 1630-2740 ohm when hot 2065-3225

I would just replace it

Excellent! Thank you for the quick response! That's what I was thinking, based on my searching and specs on other 2-prong types, but I couldn't find info specific to this engine. I've got a Denso model 116-1109 on order, should be in Friday. Fingers crossed. :)

Hi. Hoping to get an update on this relatively new post. I am having similar issues with my 1996 4runner. But I don't have a CEL code. My truck loses power at 2500 RPM. I replaced fuel pump recently. Ruled out MAF. Ruled out EFI and CO relays. I replaced all injectors, plugs and wires less than 5000 miles ago.

Did replacing the crank sensor fix your problem completely?

Hi ssspacely, it did not. Sorry for the long delay in responding, for some reason I didn't get an email notification about your comment. I'll post some more below about my journey with this problem. My 4runner finally stopped running altogether. :brick: