355 Cam phase sensor malfunction

All I can says is, as I stated before, and as stated in the PDF I posted, the signal at the coil primary indicates the ECU is grounding it but the secondary is discharging to ground through a finite resistance, not across the spark plug gap. The ECU is telling the coil to fire but it doesn't make spark. That's not a crank sensor issue.

Is it possible the problem is elsewhere? Sure, but until the high tensions side of the ignition is found 100% faultless, beyond a shadow of a doubt, that's where to look.

But I'm an old man and nobody listens.

 

I hear you but with the questionable skill of O scope use presented I default to low hanging fruit.

 

Difficulty syncing the trace or selecting the time base or vertical scale won't change the shape of the captured pulse. It definitely shows the behavior of an RL circuit decay. If it looks like a duck......

All I'm saying is its a path to follow. If it turns up blank, no harm. But to ignore a red flag because you are color blind, well....

 

This reminds me of a story my old boss (radio technician) was telling me of when he was visiting his mother in intensive care. The doctors were worried about an anomaly in his mother's heart rhythm shown on the heart monitoring equipment. My boss recognised the anomaly as a poor connection in the wiring. He played about with the wiring connections for a few minutes and the anomaly disappeared

 

Welcome to the club

Could fouled spark plugs, poorly gapped sparkplugs, engine coolant leak, too much fuel, etc, cause this finite resistance?

If the ECU can't control the fuel/air ratio, will it shut down the bank? Should we be more focused on the O2 sensors (as faulted in Grant's earlier message):

https://www.ferrarichat.com/forum/posts/146606860/

 

The frequency of the signal will not affect the quality. You just have to adjust the time/div setting if you want to get more than one pulse on the screen.

I defer to the experts, but the delay may only be active if you have the top switch in DELAY (rather than NORMAL). I think it will allow you to find the pulse manually, rather than allowing the automatics to detect it.

 

The cam turns at 2 revs per second is 2 Hz, which makes the crank turns at 2x that or 4 Hz. Which makes the starter cranking the engine over at 240 RPMs (revolutions per minutes). That is not slow for a starter.

2Hz signal is 1 pulse every 500 milliseconds.
To capture 2 pulses on one screen, you need to capture 1 full second.
You have 10 division per screen, so each division needs to be 100 millisecond.

So adjust the time division to be 100 millisecond or 200 milliseconds.

 

If the signal is weak due to high resistance in the circuit, you may have to reduce the voltage increments to make the pulse look bigger on the screen. I don't know if your test wires/crocodile clips and earths have unusually high resistance.

 

Good point. I guess, however, if the upstream oxygen sensor is faulty and saying that there is not enough fuel in the air/fuel mixure, then the injectors might be pouring unnecessary fuel into one bank. I don't know what happens when O2 sensors go bad. Do they usually slowly register a too lean mixture and keep adding fuel? However, I don't know why both upstream and downstream O2 sensors would suddenly show out of tolerance... unless there was an earthing or power issue.

Anyway, since you seem to have a hard fault on the cam sensor signal, I guess we should focus on that.... and then try to guess why it isn't affecting both banks. When you were checking the cam sensor at the ECU, what was your earth probe attached to? Some metal parts on the F355 are not always grounded to the chassis.

 

Maybe a summary in due. Hard to filter though 13 pages.

Cam sensor DTC, and CEL

Observed no spark on one bank.

1) Replaced cam sensor
2) replaced coil
3) checked continuity of wires to ECU
4) replaced ECU
5) Measured impedance of plug wires on bad side
6) Observed coil trigger signal on one pin of bad side
7) have not been able to check cam sensor signal
8) CEL has not returned (perhaps due to car not running long enough)

What is known:

Coil trigger signal looks bad.

 

After reviewing what has been done on this thread, I'm somewhat confused... The engine will run, but only on one bank and there is no spark on the other. You swapped the coils and wires from one bank to the other and still no spark? I know you have a cam sensor code that keeps popping up, but I would stay on the "no spark" diagnosis first. My experience with crank/cam poor or no signal always results in a no start. Your car does start. I would check and recheck the basics, power/grounds connections etc. I cannot tell you how many times I was completely stumped on a no spark only to find it be something like a bad ground or a poor connection on a multi-pin connector.

 

When in doubt, go to the source, Bosch, on the 5.2 system:

Crank sensor:

Cam position sensor:

I know I sound like a broken record. But as I have said, a bad crank senor means a no start. Note that unless extremely low or high voltage comes from the crank sensor, the ECU doesn't care. It's just looking for the timing. {JK: the magnitude of the voltage is dependent on RPM which is why the ECU doesn't look at }

In opposition, a bad cam sensor will not stop the engine from running. It may not run correctly, but it will start and run.

Finally, in combination, what the crank and cam sensors are saying is whether or not the ignition should fire, and when. The point is that Grant is not seeing a "if" condition. He may be seeing a "when" condition, but being off on "when" for one bank and not the other seems unlikely. And being off on when doesn't correlate with no spark, or with the shape of the coil trigger signal. The problem is summarized in the figures below. At the top left is a bad trigger signal. Top right a normal signal. The bottom left is Grant's trace. It sure looks like a bad signal to me. I have suggested he verify this by looking at the trigger signal on the bank that runs to confirm that it's different. Assuming that was to bare out, that the signal looks bad on one bank should not be a crank or cam sensor problem on a car that runs off one bank. If I'm wrong, I don't care. It would just mean that leaf has been turned over.

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Already done, John. Does this look normal?

https://www.ferrarichat.com/forum/posts/146618347/

To add to your list...

9) rotor on cam checked tight
10) 12v power present at cam sensor
11) 12v power present at centre pin of coilpack

In Grant's last tests, he could not get the car to start (which adds to the confusion). The engine is cranking at a reasonable rate, so it's probably not the battery. Do we need to recheck the left bank ignition trigger to see if we have lost ignition completely?

Would improper combustion in the engine cause that bad oscilloscope reading... or does the problem have to be electrical (i.e. that resistive element you mentioned).

 

Excuse me for not keeping up on things. I do recall the direct 12V connection to the coils and the check for 12V at the cam sensor. I was going to suggest checking the cam rotor. Glad to see that it was done.

The signal on the running bank looks reasonable to me. Since the car now won't start I would just check spark on the previously good bank with one of those flashing pen things. Could be from starting and running a short time the plugs got fouled. Could be that they are fouled on the bank that started the problem. Have they been pulled?

Not 100% sure on your last comment but there is no spark, so no "improper combustion". But AFAIK, the wave form is indicative of a resistive path to ground. That's a red flag to me. That's why I keep hammering away on this point. I don't know of anything else that would do that with the exception of, maybe, limiting the current through the primary. But that would also mean excessive resistance on the primary side, like a bad ground. However, I'd be be pleased to be wrong here 'cause it has me baffled. But based on the info from Bosch I can't see the phase sensor causing a no spark. Other running problems, yes. Could it be something as simple as fouled plugs? The crank sensor could, but not on one bank. Now that the car won't start are all it's even more confusing.

I'm going to step back on this because I don't really have anything else to offer other than what I have.

One last thing is that it doesn't surprise me that a CEL has not reappeared. It takes a while for the ECU to recognize a problem and then it has logic to validate the problem. Without the car running for some time this may not occur.

So I commend all the efforts here but something here just doesn't make sense to me.


One other thing, I have an experiment I want to do and will report back.

 

Well it look like someone has already done what I was going to experiment with.



So what I was thinking was:
1) disconnect the coil from the ECU.
2) for safety, disconnect the ECU form everything.
3) connect 12V to the center pin on the coil.
4) connect a wire to either pin 1 or pin 3 of the coil.
5) Place a flashy pen on one of the correct leads for the side of the coil being tested.
6) momentarily ground the wire from pin 1 or 3 and see if there is spark. i.e. the flashy pen thing flashes. If not, since the coil is known to be good, the problem is with the high tension leads or the plugs. If there is spark, the high tension side is good.

Test at your own risk.

And make sure the car is in neutral just incase there is a charge in any cylinder that might fire.

 

It may and it may turn the engine backwards so it would be better to remove the spark plugs and the fuel pump relay and crank the engine briefly to expel any fuel vapuors.

To test the ignition coil of the type used in the 348/355, in the described way, you will have to use a current limiting large ceramic resistor (~0.8 Ohm, at least 50W) inserted in the +12V line to the Pin 2 of the coil. This is necessary as the modern ignition coils have just 0.5 Ohm primary resistance which would cause too high current through (some 25 Amps) if not limited - big spark on connection and a risk of coil overheating. In normal operation, the current through the primary of these coils is electronically limited to some 10 Amps.

Also, grounding Pins 1 or 3 with a piece of wire will not produce strong spark but probably just about 50%. To get the full spark intensity in this way, you will need to permanently connect a capacitor of about 0.2 uF (non-polarised, i.e. non-electrolytic) between the ground and the end of the wire you are going to touch the ground with. You can use the classic ignition condenser, if you have one. Touch the ground and pull away fast.

 

Sorry if I've asked this before, but what have you been using to check for sparks? One of those $10 pen thingys?

Did you have trouble squeezing the leads into the channel when you put the coverplate back on (the last time you changed them)? What brand were they?