Alrighty just bought a 02 sl2 for my friend it has a no spark condition with neither of the two coils having any power, all grounds have been check, all fuses are good, so I was wondering if it could be a pcm or maybe I'm just missing something, FYI it is connecting to a scan tool, and has no codes, does show rpm when turning over.

 

This is usually the CKP (crankshaft position sensor or the signal from it not getting to the PCM.

If the PCM does not see a CKP signal, it kills spark AND fuel injector pulse so that there is no way for the engine to fire, as the crank position in its rotation is unknown and you don't want cylinders firing when you have no idea where the pistons are in their travels.

So you should NOT find a gas fouled plug when you pull a plug. If your injectors are leaky there might be some gas smell, but the default mode for saturn S car startup is incredibly rich to the point that it reeks of gas during startup.

There is a CKP code; have only ever read 1 post where it actually set. The code never sets.

--------

Pull the connector off the CKP and measure the resistance of the CKP at the connector -- resistance should be 500-700 ohms.

A failed CKP usually reads open circuit (infinite resistance).

 

Tested the sensor read really low and would constantly read ol so I'll replace that and let ya know what happens, thanks

 

Changed crank sensor and that did absolutely nothing nothing. Still no spark.

 

I would suggest a compression check if you have never heard it run.

 

Any updates?

Did you measure resistance for the new CKP before installing it to ensure you didn't get a dud?

 

Yup checked all of that, I'm really thinking it's the pcm.

 

A) Could also be the ICM (Ign Cntrl Module that sits under the coils. They don't go bad that often but I have changed one myself.

But start simple:

1) Are you POSITIVE you have ZERO spark being generated in the ignition?

I reviewed the previous posts. You never indicated how you determined no spark. Not trying to be insulting, but some of the answers we've received when trying to help people troubleshoot are ....entertaining.....

2) Check the coils and the ICM at the same time by:
a) waiting till nightfall
b) pop the hood
c) pull all 4 wires off the coil plugs, REMEMBERING WHERE THEY CAME FROM.
d) have a buddy hold the key to CRANK a few seconds at a time. Each coil pack should have an arc going between its terminals alternating between the two.
e) what plugs are in there and what's the gap?
f) put the plug wires back on (firing order on the sticker on front cross member)

If you see the arcing between the coil towers, you know the CKP is feeding a signal to the PCM and enabling spark. That doesn't necessarily mean that the spark is occurring where it should.

------------

If no arc


I'd trace the wires from the CKP back to the PCM. If the signal is not getting to the PCM then the PCM will not allow spark. Period. It's been a long time since I looked at the pinout on the newer S car PCMs but I will have a look if you 'd like me to.

The only complication is that the sensor output is a square wave, so you either need an oscilloscope or an older analog voltmeter to see the V change with time. There must be a spark enable output on the PCM or no spark.

Ign Cyl/BCM/PCM/Passlock

Another possibility is that the BCM and PCM are not communicating with each other. The 3rd gen s cars got BCMs and Passlock II to ensure minimum reliability.

1) The ignition has to have the right key (to activate sensor inside ign cyl)
2) the ignition cyl confirms this to the BCM
3) the BCM sends a request to the PCM to enable the fuel injectors through the Class II serial data line with the password.
4) If the message never gets to the PCM it will of course never answer--no fuel
5) If the message gets from BCM to PCM but the PCM never responds or responds improperly to the BCM's request --- no fuel


What's the status of the security light with the car of and the security system armed, and what is the state of the security system light with the key held to "CRANK"?

Awaiting your answers

 

It's been so long since I had a Saturn, that I don't remember if they have an IOD fuse or not. If so, you MIGHT want to check that. If not, I don't have a clue.

 

Rube,

Will you stop making such obvious suggestions?

There is indeed a DIS (Distributorless Ignition System) fuse.
'
This would have been next on the list if you saw no arcing across the coils. I like to back track through circuits when troubleshooting something where there are multiple failure point possibilities.

Hell, try this:
A) Six pin connector:

1) Disconnect the six pin connector from the ignition module (ICM)
2) Key ON (Engine OFF)
3) Measure V on the PNK/BLK wire (vs ground).
No other pins on the six pin connector are ground, so you must find a suitable nearby ground running to a splice pack or a good ground.


Should see 12V DC (Battery voltage). If no voltage present, indeed check the DIS fuse (pretty sure in the Underhood Junction Box (UHJB))

B) IF 12V DC V present:
1) Disconnect 5 pin connector from ICM
2) Check the RESISTANCE of the ground (BLK/WHT) wire to ground. Should be 200 Ohms.
Assuming that is good:
3) On the HARNESS side (not connector), measure the RESIStANCE between YEL and PPL wires. Should be 700 to 900 Ohms. (It is saying basically that the R you measure here should be the same as the CKP resistance. They say 700-900, I have 500 - 700 in my head -- I will defer to the manual)
4) If resistance ok, set your DVM to AC V and measure the AC V betw the YEL and PPL wires while someone cranks the engine. It should be over 200mV. IF not, replace CKP.

If all tests are ok, check the PCM connectors and pins for corrosion, etc.


There is one other remote possibility which is that the reluctor ring on the crank is damaged or has shifted such that a strong enough signal is not being generated in the CKP


Have you checked IGN 1, 3, and 4? and 2?
Pulled n tested not just while in the fuse box?'
I think 1 feeds the DIS circuit among other things.


Courtesy of Chilton 62300 Saturn Coupe. Sedans, Wagons 1991-2002.

Personally, I find this book covers the basics across the range but sucks for any in depth troubleshooting. Has a great "typical layout" for 95 and older PCMs (OBD I) too.

Aside from OBD I to OBD II changes and vac to linear EGR, MOST of the guts of the car remained unchanged through 97.

Which is why I use my 91-93 Chilton's S car manual to troubleshoot my 95 and 97 SC2s. Most of the wiring down to the color is identical. Not 100%, but works for me.