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Discussion Starter · #1 ·
I have been discussing on the forums the past few days about a knock my 9000 has been having. I finally got around to installing a knock light, but im not sure if it works.
Either i have no knocks, or the light doesnt work :p though it does flash briefly when i first start the car so thats a good sign.

Anyway, I was curious if anybody knew the operating voltage for the knock control, and what the knock voltage has to be for the computer to pick it up. According to the Tech 2 I have, I typically run around .38-.95 volts, though it spikes to 1.56-2.10 volts occasionally, though during these the knock light stays off. Are these considered knocks or are they too small?
 

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I believe the ECU has a speed density table for knock voltage threshold. 0.5v may indicate normal operation under one set of conditions and knock under another.
 

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The Trionic uses the spark plug gaps to detect the particular ionization of combustion gas when detonation occurs. There is no knock sensor per se, unlike earlier engines using piezo electric effects.

Where are you picking up the signal?

More important, why do you think you have a knocking problem?

The DI picks up and deals with detonation long before it becomes audible.

My guess is the DI cassette either works or it doesn't.
 

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The signal is picked up from pin 8 (from memory) on the 70 pin ECU connector.

This pin grounds when knocks occur, so if you use an LED, (not a normal bulb) get a 12v supply to one side of the led, and then connect the other side to pin 8 you have a knock light.
(T5 suite Trionic Documentation in the appendices)

McMuffin, yes it should flash on key turn on. Do you have it placed so you can easily see it when driving normally, or do you have to look away to see it.
 

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The pin rawill mentioned is not the voltage shown by your scan tool. Does the ECU have a current limiting resistor on this pin?
 

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Does the ECU have a current limiting resistor on this pin?

I am not sure that it does, but I think a good read up on this subject over on the ecuproject will show that some put a resistor in the line somewhere. I think some do not bother with it.
 

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Good info on the Ignition Coil Pack as utilized by the Trionic system (knock control is discussed near the bottom) :



Ignition
The ignition discharge module is mounted on the camshaft cover over the spark plugs. There are 4 ignition coils in the ignition discharge module, the secondary windings of which are connected directly to the spark plugs.
The ignition discharge module is supplied with power (B+) from the main relay and connected to ground at grounding point G7P.

When the main relay operates, power (B+) is supplied to the ignition discharge module which converts 12 V to 400 V d.c. and charges a capacitor with it. This voltage (400 V) is connected to one pole of the primary windings of the 4 ignition coils.
Four trigger leads are connected to the ignition discharge module from Trionic ECM pin 9 (cyl. 1), pin 10 (cyl. 2), pin 11 (cyl. 3) and pin 12 (cyl. 4).
When the engine control module grounds pin 9, the other pole of the primary winding of the ignition coil for cylinder 1 will be grounded (via the B+ input of the ignition discharge module) and the 400 V transformed to a maximum of 40,000 V. Ignition for cylinders 2, 3 and 4 takes place in the same way.
If there is an open circuit in the power supply or a ground connection to the ignition discharge module, the engine will not start.



Ignition Control
On starting, ignition timing is 10°BTDC . To facilitate starting when the coolant temperature is below 0°C , the electronic control module will ground the relevant trigger lead 210 times a second from 10°BTDC to 20°ATDC , which gives rise to the "multispark" function. This function is discontinued at engine speeds above 850 rpm.
A special ignition control curve is used at idling speed. Normal ignition advance is about 0-8° , depending on the engine version.
If engine speed drops, as may happen when the radiator fan cuts in, the ignition timing will be advanced to a maximum of 20°BTDC to increase engine torque and restore engine revs. Similarly, the ignition will be retarded if engine speed increases.
Ignition control during idling compensates for rapid changes in engine idling speed.
When the throttle position moves away from idling, ignition control changes over to normal control depending on load and engine speed.



Combustion Signals
The Trionic system does not have a camshaft position sensor. A camshaft position sensor is normally required for sequential knock control and fuel injection.

The Saab Trionic must decide whether cyl. 1 or cyl. 4 is firing when the crankshaft position sensor indicates that cyl. 1 and cyl. 4 are at top dead centre.

This is done as follows:
One of the poles of the secondary windings of the 4 ignition coils is connected in the usual manner to the spark plugs. The other pole is not connected directly to ground but to 80 V . As a result, 80 V is always present across the spark plug electrodes except at the very moment a spark is produced.

When combustion takes place, the temperature in the combustion chamber is very high. The gases are ionized and start to conduct current. This means that a current passes across the spark plug gap (without producing a spark).




The ionization current is measured in pairs, cylinders 1+2 and cylinders 3+4. If combustion takes place in cylinder 1 or 2, the ignition discharge module sends a pulse (B+) to pin 17 of the Trionic's engine control module. Similarly, the ignition discharge module sends a pulse (B+) to pin 18 of the engine control module if combustion takes place in cylinder 3 or 4.

If the crankshaft position sensor indicates that cylinders 1 and 4 are at top dead centre and a pulse (B+) is applied to pin 17 of the engine control module at the same time, then the engine control module knows that cylinder 1 has fired.

When the engine is started, the ECM does not know which of cylinders 1 and 4 is in the compression position, and ignition consequently takes place on both cylinders 1 and 4 simultaneously. In the same way ignition takes place on cylinders 2 and 3. As soon as combustion signals arrive on pins 17 and 18 of the ECM, both ignition and fuel injection are synchronized to the engine firing order.

On M96 and later models (On-Board Diagnostic II), combustion signals are also used to detect misfiring.

In the event of an open circuit in either of the leads connected to pins 17 and 18 of the electronic control module, no synchronization of ignition timing or fuel injection will occur. Knock control will take place at the same time on cylinders 1+4 and 2+3.



Knock Control
The Saab Trionic does not have a conventional knock sensor. Instead the ignition discharge module analyzes the ionization currents for all the cylinders and sends signals to pin 44 on the Trionic ECM, This function is adaptive with respect to upsetting fuel additives.

From the combustion signals the engine control module knows which cylinder has fired and if at the same time the knocking signal is above a definite level, the control module records knocking on that cylinder. The ignition timing is then retarded 1.5° on that cylinder.

In the event of persistent knocking, the timing will be retarded additionally but not more than a maximum of 12° . If ignition timing is retarded by more than a certain amount on all cylinders, the quantity of fuel injected will be slightly increased.

If knocking occurs when intake manifold pressure is higher than about 140 kPa , knock control will take place in a different way, as follows:
first the fuel injection and ignition matrices are changed and if this does not help then boost pressure will be reduced.
The aim is to achieve good performance even in the event of knocking.
In the event of a break in the lead connected to pin 44 of the electronic control module, basic boost pressure will be obtained and ignition timing retarded by 12° when the engine load is so high that knocking could occur.



Burn-Off
After the ignition switch has been turned off and the engine has stopped, the main relay remains activated for a further 6 seconds. The Trionic ECM then grounds all the trigger leads 210 times per second for 5 seconds. Each electrode gap **** off impurities with more than 1000 sparks.
 

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P0327

More detailed explaination:



Symptom Of Fault .
The car runs on basic boost pressure only, continuous: ignition retard.

NOTE: The Saab Trionic system does not have a conventional knock sensor. The signal comes from the ignition discharge module.

Conditions .


  • Engine running
  • No knock signal for 10 seconds.
Diagnostic Help .
A knock signal reading can be obtained using an ISAT scan tool.

  • Select "READ FUNCTIONS".
  • Select "KNOCK SENSOR".
The ISAT scan tool should show a reading of between 0 and 2.55 V , depending on the level of the knock signal. At idling speed the ISAT scan tool should show a reading of 0.06-0.16 V . If the throttle is opened suddenly, the ISAT scan tool could show a reading of 0.06-2.55 V .

In the event of a break in the signal lead connected to pin 44 of the control module, a reading of 0.06-0.08 V will normally be obtained whatever the throttle opening.



Diagnostic Procedure .


  1. Check the electrical interface
    • Ignition switch in ON position.
    • Unplug the ignition discharge module's 10-pin connector.
    • Connect a multimeter, set for d.c. voltage, to
    • connector pin 7 and battery positive (B+)
    • B- connector pin 7 and battery negative (B-) The multimeter should be connected alternately to battery positive (B+) and battery negative (B-).
When connected to battery positive (B+), the meter should indicate a positive voltage (about 6-12 V ) which rapidly drops to 0 V .

When connected to battery negative (B-), the meter should indicate a negative voltage (about -6 to -12 V ) which rapidly rises to 0 V .

Are the readings obtained OK?
YES:

  • Continue with point 3.
NO:

  • Continue with point 2.


  1. Check the knock signal's lead
    • Check the continuity of the lead between pin 7 of the ignition discharge module and pin 44 of the control module.
    • Check the lead for open circuit and shorting.
Are the test readings OK?
YES:

  • Continue with point 3.
No

  • Rectify the fault and proceed to point 3.






  1. Final check:,
    • Clear the diagnostic trouble code.
    • Implementation of driving cycle: Drive the car at varying engine loads and rpm for 5 minutes.
    • Evaluation of driving cycle: Check whether the diagnostic trouble code has recurred.
Has the diagnostic trouble code recurred?
YES:

  • Try fitting a replacement ignition discharge module and, after a repetition of the driving cycle, check whether the diagnostic trouble code is generated afresh.
NO:

  • The remedial measure taken was correct.
Has the diagnostic trouble code been generated afresh after changing the ignition discharge module?
YES:

  • Refit the original ignition discharge module and then continue at "Before Replacing a Control Module". See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics
NO:

  • Scrap the original ignition discharge module. The remedial measure taken was correct.
 

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Excellent
 

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Discussion Starter · #11 ·
I know this thread is old, but it seems my knocking issue has returned. When going up to full throttle, past 4k rpm my knock light flashes steadily and sometimes stays solid, though no knocks are audible.

I did replace me spArk plugs 2 days ago, and used the same NGK BCPR7EIX Iridiums that I've used for a year and a half or so, because they seem to be better with the high boost.

My question, I know the knock signal is gathered from the plugs. If they are not gapped properly, could that be my issue of knock/potentially faulty signal?
 

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I would be surprised if an incorrect gap would do it.

However, if the old plugs were working fine, I would swap them back in and do a test.

I would also be thinking about a restricted inlet, and or exhaust, but that does not make sense if all was well before and all you have done is changed plugs.
 

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Discussion Starter · #13 ·
Well I can't really do that, I replaced the old plugs due to a misfire issue. Two of the plugs cracked on the ceramic...
 

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Mmm, not sure what to suggest to check the knock light issue, given it was fine before you changed the plugs.

Maybe take the aircleaner element out and see what happens.
Just a test, I don't really think it will make any difference.
 

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Discussion Starter · #15 ·
Well it started doing this a few days before I changed the plugs, but I figured it was in tandem with the misfire/cracked plug. It's just slightly worse now that I've changed them.
 

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How did the spark plug crack? That's very, very unusual. In fact, I never saw one crack spontaneously in my 27 year career fixing cars.
I'd bet your DI cassette is dying, but an internet diagnosis is worth what you pay for it.
 

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Discussion Starter · #17 ·
I've been a technician for a measly 5 years and I've neer seen it either. The plug on 1&2 cracked from the bolt head up to the top of the electrode on two sides, directly opposite from eachother
 
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