CAM Sensor on a 1997 Saturn SL2

Tiny
PASTOR ANDY
  • MEMBER
  • 1997 SATURN
I have a 1997 Saturn SL2 (1.9 L?) Anyway, the service engine soon light comes on every so often for the same thing. Cam sensor. But the shop I went to did some research on it and found that my car doesn't have a cam sensor. So each time I take it in, they find that code, then just clear it. But it still continues to come on.
Any ideas on what I can do to get it to stop triggering the service engine soon light? Also, I find it odd that the car would continue to trigger a code for something it doesn't have. Any info on that? Because if it really DOES exist, then I'd like to get it fixed before it turns into something real serious.
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Wednesday, February 21st, 2007 AT 10:40 PM

4 Replies

Tiny
KIN CHAN
  • MEMBER
This is challenging.I think I've heard of the cam sensor issue in 1 of my class. Email me more info.I'm not at the shop now. So ican't look up ur cars system to tell u whats goin on. But OBD2 sys should be fairly straight forward to figure it out.
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Thursday, February 22nd, 2007 AT 4:23 AM
Tiny
PASTOR ANDY
  • MEMBER
I'm not sure what else to tell you, really.
It's actually my second engine. My first one's cam broke, locking up the engine after about 22,000 miles (which I wasn't too happy about, especially since that engine seemed to give off more torque than the one I have now).
So when I hear of a cam sensor, I'm cautious about that happening again. Only, I didn't get such warnings with the first one.
This one, for some reason, gives off the same code of it being the cam sensor. The mechanic checked it out online and it turned out that my car (according to his source) doesn't have a cam sensor. So why it's giving off that code, nobody can seem to figure out.
And I know that Saturns have issues, but really, ever since I stopped taking it to the dealer for repairs, it's been a GREAT car! (Seriously!)
So I love the car, and would really like to fix whatever's setting off this problem.
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Thursday, February 22nd, 2007 AT 10:12 AM
Tiny
PEPPERMRJ
  • MEMBER
No cam sensor on your satty.
Here is all you need to know about the ghost cam sensor and it's fault codes courtesy of a very good saturn tech, Sierrap615.

"Most of this came from TSB 98-T-49A, and a few of my tips thrown in.

Both P0340 and P0341 both relate to the Camshaft Position Sensor(I will just call it Cam sensor from now on), the only problem is that the S-Series engines don't have a Cam sensor, not a typical one at least. Instead, the DIS module watches when the #4 spark plug fires on the compression cycle and fakes a Cam sensor signal from it. The tricky part is that on a DIS waste spark system, spark plugs fire with their mated cylinders(1/4 and 2/3 in 4 cylinder engines) every time the cylinder is at TDC, regardless of weather the cylinder is on exhaust or compression. However, it takes far more voltage to fire a spark plug on the compression stroke then on the exhaust stroke, due to the compressed air(more air molacules, more air the spark needs to jump, more resistance to spark). The increased voltage needed on the compression stroke is detected by the "#4 sensing circuit" inside the DIS module for the Cam sensor signal. If the resistance of the secondary system is not in the proper range or something else is affecting the voltage draw, the "#4 sensing circuit" will be unable to work properly.

In short, anything worng with the ignition system, bad Cam sensor signal.

Next for the diagnositic, i'm converting this from a graphic map to a text format, so bear with me.

Step 1: remove secondary wires from spark plugs, keep the wires on the coil. Measure resistance from #1 wire to #4 wire and then #2 wire to #3 wire. Resistance should be 11k ohms to 45k ohms(YIKES thats a wide range)

If resistance is in specs, go to step 2, if not in specs, go to step 3

Step 2: remove secondary wires from the coil packs. Check for corrosion on the towers and wires.

If there is corrosion, go to step 4

If not, go to step 5

Step 3: remove secondary wires from the coil packs. Check for corrosion on the towers and wires.

If there is corrosion, go to step 4

If not, go to step 6

Step 4: Replace or clean coils and/or wires as nessaciry. Retest to confirm.

Step 5: Remove spark plugs. Check for carbon or abnormal wear and proper gap(0.040 in)

If plugs check out good, go to step 8.

If the plugs are bad, replace as needed and retest to confirm.

Step 6: Measure resistance of individual secondary wires. Specs are 1.5k ohms to 15k ohms ( thats what this chart says, but my knowage says 8k ohms is normal, greater then 12k ohms should be replaced)

If wires are in spec, go to step 7

If wires are bad, replace as needed and retest to confirm

Step 7: Measure resistance from tower to tower on the coil packs (hold tight for good reading). Spec is 8K to 15K.

If coils are in spec, go back up to step 5

If coils are bad, replace as needed and retest to confirm

Step 8:(90% of the time I bet the problem is solved by now) Start engine. Perform underhood visual inspection of the ignition system, check for arcing(best done in a dark area, if you are inside a garage, besure the exhaust is vented). Wet DIS module, coils, and secondary wires with salt water to provide optional ground path.(Arcing from the wire boot to the valve cover is possible, but would be hidden)

If arcing is present, replace wires or coils as needed and retest to confirm.

If not, go to step 9.

Step 9: Turn ignition off, backprobe J3D03 (Circuit 633, brn/wht wire) at PCM with voltmeter. Connect other lead to ground. Turn ignition on, engine off. Measure voltage.

Less then 4.5 volts, go to step 10
4.5-5.5 volts, go to step 12
more then 5.5 volts, go to step 11

Step 10. Check connections in circult 633, repair short to ground, retest to confirm

Step 11. Repair short to voltage in circuit 633, retest to confirm.

Step 12. Start engine, at idle observe voltmeter

less then 2.0 volts, replace DIS module, retest to confirm
2.0 - 4.0 volts, problem intermittent
4.0 - 5.5 volts, go to step 13
more then 5.5 volts, go back up to step 11

Step 13. Turn ignition off, backprobe circuit 633 at DIS module with voltmeter, other lead to ground. Check voltage.

4.0 volts or less, repair open/high resistance in circuit 633, retest to confirm.
Greater then 4.0 volts, go to step 14

Step 14: Inspect terminal on DIS module for looseness or poor connection.

If terminal is bad, repair it
If terminal is good, replace the DIS module.

Thats all of the diagnoistic chart, anybody who has done this in the past feel free to throw in your tips/opinons. I would like to add three things:

1. Check the grounding bolt on the DIS module for corrosion.
2. Besure the secondary wires are fully seated, you should feel/hear a click
3. Use dielectric grease on the coil towers"

Good luck and let us know. :)
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Sunday, February 25th, 2007 AT 9:58 PM
Tiny
KIN CHAN
  • MEMBER
Thats the part I heard of. This is a wacky forum. I don't know how we address an issue when some1 ask a really technical symptom. Ither to detect or repair. If we should explain more about cause or fix. Fixing parts is the hardest. Like this case here. If a mechanic get this piece of info. Then its easy. Oscilliscope the primary and secondary with KV & low amp probe for coil integrity. Pretty much can identify which part is the offender without even go thru that 12 points procedure. But the problem is most of these question were ask by some1 who doesn't even know the structure of OBD2. The cam sensor signal is used or must have to generate or avail for the misfiring code which is mandatory by OBD2 system. Ahhhhhhh. This is driving me crazy
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Monday, February 26th, 2007 AT 6:18 AM

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