Disconnect the TCM first. That"ll take out the speed sensors. Test. Measure the resistance of the cam and crank wires to A4. Should be about 0.01-0.02Ω. If that's normal take new dedicated ground wires for the cam and crank and put them on as the only thing on A4. That'll take out everything on K167 ground.

 

?

 

both ckps and cmps were .06-.08 on 200 ohm setting. Same as before, that's the range all my signal, power ground ohms to pcm plug one. I did unplug the T.C.M.

 

Everybody and their grandmother shares A4 as their ground (see below), but the speed sensors have been reported to have a relationship with the crankshsaft sensor so IMO is worthwhile to pull out of the equation separately. Cut A4 and connect only the crank and cam sensor to it. Measure resistance of the new devoted wires. See if 1391 disappears.

Ooooh scary thought. If this does work then you have to go through that whole mess and figure out which sensor or circuit is causing the problem. Good luck on that.

After this really need the oscilloscope.

 

Time to regroup!

After rereading the thread, not only must this be a frustrating problem for you, but frustrating answering the same questions all the time!

Sorry for asking about the alternator when you mentioned that before.

Forget that. If

then maybe it's a little high cause the wires are in circuit, but wanna measure a 3 foot piece of that 16 ga. wire before you put it in?

Did you test the camshaft position sensor signal for voltage while turning the engine over (by hand to see if you get 5.0 +/- 0.25V and 0.0)?

You still got that 0.05 residual voltage on the crank sensor to address (when you were looking at reluctor windows). I really think that needs to be 0.0.

Did you already put in new devoted signal wires?

BTW when measuring voltage use the 20V range instead of the 9V. It looks cooler.

 

unfortunately for testing purposes, disconnecting each sensors will throw code/s

I dont know which sensors can be disconnected and still allow the engine to start and run at all

have you done research on the P1391 code on NAXJA..and Google, to see if anyone has had a persistent code before?

after that it does come down to an experienced auto tech with expertise on a scope

 

.

 

No that's fine. Since we're measuring within the circuit it's probably reflective of other stuff in the circuit. The only way to truly get an accurate reading of the wire is pull it out. Taking a known length and gauge of wire will allow us to see what your multimeter SHOULD be seeing, and that should be about 0.01. As long as we're not seeing something considerably more than that.

 

We don't care. As long as 1391 disappears. We know we're going to generate more codes.

We don't care about that either. 1391 is also a cranking code, so as long as we generate 20 events on 2 successive trips the code will appear if not corrected.

 

IMO that's the #1 suspect now, PCM wants to see 0.0.

 

I mean, if we get an oscilloscope and all the peaks are nice and even at 5.xx and the base is 0.05, 0.1, 0.0, and whatever, then we're going to say oh look problem there!

 

https://www.ebay.com/itm/SainSmart-M...-/121590979073

Correct me if I'm wrong but a two channel can only see one sensor a a time correct? One lead on ground the other on signal?

 

I would try Dave51 latest suggestions, unplugging all the sensors except crank and cam.

also possibly be inclined to buy cheap CPS and CAM sensors to substitute

rewire, as suggested before, as a last measure

After that, I would go back to the scope technician, get prints of the expanded waveforms etc etc.

If he is not sufficiently expert to do that, you need to find someone that is...unfortunately, this is not common, and generally that person would be a qualified Electronics Engineer

 

No. A two channel oscilloscope, by definition, will read data from two sources.

But you're not thinking of getting that thing, are you?

 

there is a fair learning curve & expertise required with scopes...an auto tech ? with a scope has already said its ok ?

presumably he had the gear and expertise to do at least a basic check...but perhaps he did not look close enough at the signals, or lacked experience to analyse them

remember I mentioned to not accept his offer of a refund?,,, I have found in the past that (most) automotive experts will give free/underprice time to help resolve an issue in such a case. I cultivate & groom them lol...as if I cant or dont want to fix it myself, its usually nasty, I always offer to pay for all advice time, in cash of course

In an ideal world, you would have another running XJ to compare (like my 59 digits off VIN spare '96 XJ)