Need help interperting OBD II information

When the car doesn't start, is there fuel pressure? Yes, I know you hear the pump prime, but if you check the pressure at the rail, is it good?

How did they check it? It could be intermittent. Clearly whatever is bad is intermittent, and the position sensor is the first thing I'd have swapped.

The OTHER reason you could get that error code is if you have some other position sensor (sometimes an RPM sensor, etc.) which is disgreeing with the crankshaft sensor.

I have no graphics here, but given the basic behaviour, I'd have swapped the position sensor out. If it turns out not to be the problem, well, now you have a spare in the garage.

--scott

B1S2 fuel trim reads 99%

that is way out of bounds for a normal engine.

Correction to #2, the temp is 170, not 160.

Thanks,

Sam

snipped-for-privacy@yahoo.com wrote:

I dont know much about O2 sensors. Are there actually two physical sensors? B1S1 & B1S2?

Thanks,

Sam

Lawrence Glickman wrote:

Not sure how they checked on the crankshaft sensor. I have not checked fuel pressure, usually it happens at the grocery store or the side of the road and I can't do any testing. =(

Scott Dorsey wrote:

On my Vulcan V6, the CPS is a bastard to get to. But it is =possible=, so I would buy the part and do it myself. YMMV.

No way I'm paying that kind of $$$ for a CPS swap. Not in this lifetime.

Yes it would be a PITA. Yes I could do it. Might take an hour, going in through the top of the engine bay. Might take less time if I could get at it from under the vehicle. Either way, I would buy the part and try some acrobatics to see how I could get to the sensor, which on my engine, is just held in place with one lousy screw. Getting to that screw is another story.

Lg

I feel your pain. The CPS is behind the harmonic balancer. You have to take that off to get to it.

Lawrence Glickman wrote:

On my vehicle Sam, there are 2 sensors for each bank of the engine. Bank One, the bank (row) of cylinders with cylinder 1 as defined by the firing order, has B1S1 on the exhaust manifold, and then B1S2 just after the catalytic converter for THAT bank.

IOW, I have 4 O2 sensors, and TWO cat cons.

Not too hard to get to, but when I think of swapping them out, you know, it is all becoming a PITA to my old body.

Lg

My idea is to leave the HB where it is, and come at the CPS from an angle that will allow removal and reinstallation. I have all kinds of

I would swap it myself anyhow, even if I had to lie down on top of the engine, or crawl under the car. No way I have access to $380.

Lg

In 1997, GM didn't use the post cat oxygen sensor to calculate fuel trim. IOWs, it's a bogus reading.

The OP may want to purchase the enhanced software from Auto Enginuity and use it to graph the two crankshaft position sensor signals at the time of stall. (if the enhanced does in fact report the two crank position sensors as a PID) The OP may also want to verify the P0336 trouble code with a different scan tool/code reader because there have been instances of AE reporting trouble codes incorrectly. The OP should verify that there is no coolant leaking from the water pump onto the crankshaft position sensor(s).

Whenever you see that the data is not valid due to scan tool function or other cause.

Don

OK, the first thing I thought before getting halfway through your post was intermittant crank position sensor (CKP) failure.

You have spent a fair amount of $ already on parts that haven't fixed the problem. The CKP is the most likely component to cause this on your engine, followed by the ICM (replaced), followed by compromised wiring or shielding of the CKP circuit, and finally the PCM. For the cost of a CKP sensor I would not hesitate with replacing it. I think they are around $30 to $60.

I can't physically inspect your car to look at the wiring or test the circuits to verify this diagnosis but I speak from experience. It's too bad you had several mechanics supposedly test (good) your sensor and then condemn a $300+ ICM! + 3 coils!

It is difficult and time consuming to test an intermittant stall like this, but with the code P0335 you know right where to start. I would hook a 2channel scope up to the ICM connector as follows: channel 1 to the yellow CKP to ICM 18X reference wire; channel 2 to the blue/black ICM to PCM CKP 18X reference wire. You should see square waves on both wires. They should be sharp and defined. Nonsensical stray voltages would be a sign of poor shielding. The wrong number or inconsistently shaped waves would be a sign of CKP sensor breakdown on the yellow wire; ICM failure on the blue/black wire. If both signals are perfect when the vehicle dies and sets a P0336 concurrently you should suspect the PCM.

The sensor sits beside/behind the crankshaft pulley on the front of the engine. Other than loosening and tightening the crank pulley bolt, it's a fairly easy replacement. It would take a tech about 15 minutes of mechanical work to do.

NOTE: You are supposed to do a "CKP sensor variation learn" procedure following replacement. This is a simple scantool operation that requires a Tech II (GM mega$$ scanner), or a SnapOn with newer software. If I were you I just would replace the sensor, clear the codes, then drive it and monitor the MIL. If you never get a P1336 (variation relearn procedure not performed) then the new sensor is lined up close enough to be a nonfactor.

If you want to explore this relearn dealio, I would suggest you contact Jay Horak of Auto Enginuity. He designed your scan software and constantly responds to tech questions via email. Ask him if the GM software addon (about $150) has the capability to perform the CPK sensor variation learn function on a 1997 Riviera 3.8SC. He's very good about product support. I guarantee that you will be happy with the functions and data you will be able to retrieve with his GM software. His enhanced software packages can be glitchy but the reports from the field are that they get markably better and more powerful with each upgrade. One year of quarterly upgrades comes with the enhanced software package. An additional year of updates is $50 last time I checked. I figured since you already purchased the $250+ OBDII package it would be a no-brainer to buy the 'good stuff' : )

Toyota MDT in MO

When I wrote: It is difficult and time consuming to test an intermittant stall like this, but with the code P0335 you know right where to start.

I meant P0336 D'oh!

Toyota MDT in MO

snips:

Ok

money spent, and no guarantee that the *new* software is going to have a bullet proof CPS algorithm.

This is true. On my car, it would have to be a major leak. Anything short of that is going to flow away from my CPS. But the geometry of his engine is no doubt different.

I think on my car, I would buy the part ( after making certain the water pump isn't leaking onto it ), and install it myself, thereby saving labor costs. If I could not, for some reason, pull off the part swap, that's another story. But I would _have_ to give it a try first. That's just *me.*

Lg

Okay, well it caught my eye. I didn't think it looked right, so that's why I even mentioned it.

Lg

Good point! That's a sign that you do this kind of work every day : )

Toyota MDT in MO

P.S. I have no doubt his OBDII AE software is reporting the P0336 correctly given the circumstances. I think the problem is more prominent with the enhanced software screwing up FR and other GM specific historical code data. I'm really leaning towards getting AE based on the price. It's a hell of a hobby scanner if nothing else.

naaah... some days, I do front end rebuilds... ;-)

I'm pretty happy with it.

Very strong on Ford, very strong on GM, as strong as I've seen on Toyota, a little weak on Chrysler but they (Jay) say it's in the works.

No, he can call them and ask whether the crank sensor is a supported PID. If not, then he doesn't spend the money. Generic OBD2 scan data is a lot like eating a T-bone steak with chop sticks, it can be done, but it will take a long time and there will be a lot of teeth gnashing. IOWs, he doesn't know all of what he's missing not having the enhanced software.

Coolant leak from the water pump wiping out a crank sensor is fairly common on the Buick 3800.

The OP needs to be advised, the crank sensor splits two sets of shutters on the harmonic balancer, the sensor needs to be set so that the shutters do not rub, hit or in any way make physical contact with the sensor. One can buy the special tool from Kent- Moore, or he can cut two strips of plastic bottle and use them as a feeler gauge.