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Old 06-15-2021, 12:00 PM   #1
savethebees
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Default 2003 l300 no start

I think there is a problem with the BCM on my 2003 l300. The wipers and the gauges work on and off again. But would a BCM problem cause no crank and no fuel pump or would that be the ECM? How about headlights that are stuck on? I tried to replace the relay and it shut them off yesterday for awhile, but today the headlights were stuck on again until I pulled the fuses.
I'm not familiar with Saturn electronics so any insight would be really appreciated. Thanks
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Old 06-15-2021, 03:52 PM   #2
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2003 L-Series 3.0L Sedan
Default Re: 2003 l300 no start

*What's battery voltage?

*Is security (yellow car with oversize padlock symbol) flashing?

*Mileage, maintenance performed, parts replaced?

The ecm runs the EFI system to operate the engine. The bcm, excluding airbag and abs/tc) runs everything else including providing error codes thru the OBD II port.

There may be several problems. If security flashes, factory Passlock anti theft disables injector operation. Remotes Lock/enable security, Unlock/disables security. Lock/Passlock enabled - security blinks once every few seconds.

Last edited by fdryer; 06-15-2021 at 04:02 PM.
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Old 06-15-2021, 05:54 PM   #3
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Default Re: 2003 l300 no start

Now I have spark
No security light
325000 miles
battery voltage 12.35
Lights l/r fuses removed (running lights)
Now I have fuel and temp gages working for time being at least.
Do you have a pump wire diagram for this car?
By the way, thanks for answering!
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Old 06-15-2021, 05:57 PM   #4
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Default Re: 2003 l300 no start

Quote:
Originally Posted by savethebees View Post
Now I have spark
No security light
325000 miles
battery voltage 12.35
Lights l/r fuses removed (running lights)
Now I have fuel and temp gages working for time being at least.
Do you have a pump wire diagram for this car?
By the way, thanks for answering!
Oh yeah, car cranks now. Suspect battery from yesterday as being defective. I only had checked the voltage at 12.4 before I put it in and did not load check it.
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Old 06-15-2021, 06:09 PM   #5
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Default Re: 2003 l300 no start

Quote:
Originally Posted by fdryer View Post
*What's battery voltage?

*Is security (yellow car with oversize padlock symbol) flashing?

*Mileage, maintenance performed, parts replaced?

The ecm runs the EFI system to operate the engine. The bcm, excluding airbag and abs/tc) runs everything else including providing error codes thru the OBD II port.

There may be several problems. If security flashes, factory Passlock anti theft disables injector operation. Remotes Lock/enable security, Unlock/disables security. Lock/Passlock enabled - security blinks once every few seconds.
Initially I changed the the crank position sensor. No help.
Bought a throttle body and tested it. I does the same things the one on car does but neither one will hold a set position when operated from the car harness and someone operating the gas pedal. I don't know if that's normal. Seems pointless to put the replacement one in though.
This is my wife's mother's car. I don't think she has had a whole lot of trouble besides wipers working intermittently and had changed the cam position sensor a while back.
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Old 06-15-2021, 07:18 PM   #6
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2003 L-Series 3.0L Sedan
Default Re: 2003 l300 no start

Wiring diagrams are posted in previous threads. I posted them.

With security OFF, this eliminates Passlock disabling injector operation. This problem seems to lean on either a fuel or spark problem. Fuel is relatively easy to test in one of two ways while spark is tested indirectly without going thru the trouble of removing spark plugs.

At 325k miles, plugs should have been replaced three times, once every 100k miles with factory recommended plugs to have the longest reliability. If you do not have records then remove them for examination and replacement if in doubt. This isn't a regular weekend diy routine. Search for wiring diagrams and plug replacement procedures within these forums.

Fuel and pressure occur as soon as ignition is turned on with a 2 second pump cycle then shutting off if the engine isn't started. This allows a quick test for fuel pump operation and pressure by removing the fuel test valve cap on the fuel rail over the engine. Depressing the valve stem should result in a strong spray of fuel (cover the valve loosely with a rag). A fuel pressure gauge is better to asses actual pressure (39-49 psi), borrowing one from Autozone or other auto store providing loaners without charge. At 325k miles, maybe the fuel pump is announcing its demise. While rare, fuel pump failure doesn't have a time or mileage reference when they fail. Mine failed around 75k miles.

The lack of spark or fuel can be easily tested another way - spraying starting fluid into the throttle body. Supplying fuel should result in startup if spark is available. If the engine doesn't startup after spraying starting fluid, one of two issues may prevent the engine from running - a flooded engine drowning spark or the fuel pump acting erratic, intermittent or dead. Under normal circumstances, an engine failing to start (cold weather) with repeated starting attempts can flood the engine, drowning spark. The quick fix is to hold throttle wide open and starting again. This tells the ecm to halt injector operation while more air is ingested, diluting/drying out wet plugs until a sputtering startup occurs. Owner's manuals describe this as clear flood mode. Several seconds of starting is more than enough for clearing a flooded engine.

Starting fluid is the easiest method to determine a fuel or spark issue. Other methods are more time consuming and can be suggested if needed.

With ignition turned on, the EFI system is running. The ecm is waiting for the engine to physically turn over. You should be able to have someone press the gas pedal while you observe throttle plate movement in proportion to pedal travel. L300s use drive by wire throttle; pedal is electronic, feeding signals to the ecm, ecm commanding the electric servo motor in the throttle body to move the throttle plate. Pedal-ecm-throttle actuator. Feedback sensors on throttle and pedal keep the ecm informed to react instantly as if the pedal were connected to throttle with a steel cable and linkages.

If throttle plate movement doesn't occur with pedal travel (ignition switch ON), this may be another problem.
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Old 06-15-2021, 07:55 PM   #7
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Default Re: 2003 l300 no start

Quote:
Originally Posted by fdryer View Post
Wiring diagrams are posted in previous threads. I posted them.

With security OFF, this eliminates Passlock disabling injector operation. This problem seems to lean on either a fuel or spark problem. Fuel is relatively easy to test in one of two ways while spark is tested indirectly without going thru the trouble of removing spark plugs.

At 325k miles, plugs should have been replaced three times, once every 100k miles with factory recommended plugs to have the longest reliability. If you do not have records then remove them for examination and replacement if in doubt. This isn't a regular weekend diy routine. Search for wiring diagrams and plug replacement procedures within these forums.

Fuel and pressure occur as soon as ignition is turned on with a 2 second pump cycle then shutting off if the engine isn't started. This allows a quick test for fuel pump operation and pressure by removing the fuel test valve cap on the fuel rail over the engine. Depressing the valve stem should result in a strong spray of fuel (cover the valve loosely with a rag). A fuel pressure gauge is better to asses actual pressure (39-49 psi), borrowing one from Autozone or other auto store providing loaners without charge. At 325k miles, maybe the fuel pump is announcing its demise. While rare, fuel pump failure doesn't have a time or mileage reference when they fail. Mine failed around 75k miles.

The lack of spark or fuel can be easily tested another way - spraying starting fluid into the throttle body. Supplying fuel should result in startup if spark is available. If the engine doesn't startup after spraying starting fluid, one of two issues may prevent the engine from running - a flooded engine drowning spark or the fuel pump acting erratic, intermittent or dead. Under normal circumstances, an engine failing to start (cold weather) with repeated starting attempts can flood the engine, drowning spark. The quick fix is to hold throttle wide open and starting again. This tells the ecm to halt injector operation while more air is ingested, diluting/drying out wet plugs until a sputtering startup occurs. Owner's manuals describe this as clear flood mode. Several seconds of starting is more than enough for clearing a flooded engine.

Starting fluid is the easiest method to determine a fuel or spark issue. Other methods are more time consuming and can be suggested if needed.

With ignition turned on, the EFI system is running. The ecm is waiting for the engine to physically turn over. You should be able to have someone press the gas pedal while you observe throttle plate movement in proportion to pedal travel. L300s use drive by wire throttle; pedal is electronic, feeding signals to the ecm, ecm commanding the electric servo motor in the throttle body to move the throttle plate. Pedal-ecm-throttle actuator. Feedback sensors on throttle and pedal keep the ecm informed to react instantly as if the pedal were connected to throttle with a steel cable and linkages.

If throttle plate movement doesn't occur with pedal travel (ignition switch ON), this may be another problem.
Thanks. It does try to start on starter fluid. I will test for voltage at the pump when I find the diagram. I have to prove a faulty BCM is not causing the pump to not run before replacing the pump. If no voltage to pump I am thinking I would like to jumper 12v to the pump and try it. if that doesn't work I will be confident the pump has failed. Does my logic sound alright?
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Old 06-15-2021, 08:18 PM   #8
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2003 L-Series 3.0L Sedan
Default Re: 2003 l300 no start

The bcm doesn't control fuel pump operation. As mentioned previously, the ecm runs the entire EFI system. Descriptions of interaction between bcm and ecm are posted in past threads. The bcm's only role is Passlock theft deterrent; if enabled and active, flashing security indicator, the bcm sends a fuel password to the ecm. The ecm disables injector operation to prevent someone from driving away with the car. It works with the only weakness to defeat it with the ignition key if a smart thief wanted any Saturn using Passlock. The security indicator is fool proof and the only visible indicator to determine Passlock status.

Do you know if spark plugs were ever replaced? This may be a strong possibility to prevent spark igniting fuel. Search bills and records. PLease do not ignore this possibility.

If you are comfortable with wiring, you can pull the fuel pump fuse, review pinout labeling on the four or five pin relay, and jumper relay socket terminals 30 and 87; this sends 12v to power the fuel pump immediately, regardless of ignition switch position. Be aware of jumpering incorrectly as 12v sent to ground or ecm may blow a fuse or damage the ecm. When jumpered correctly, you should be able to hear a quiet hissing sound as the fuel pump pressurizes the fuel lines. Depressing the fuel test valve should result in a strong spray of fuel. Two stainless lines over the engine with the test valve capped on the feed line.
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Old 06-17-2021, 11:15 AM   #9
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Default Re: 2003 l300 no start

Quote:
Originally Posted by fdryer View Post
The bcm doesn't control fuel pump operation. As mentioned previously, the ecm runs the entire EFI system. Descriptions of interaction between bcm and ecm are posted in past threads. The bcm's only role is Passlock theft deterrent; if enabled and active, flashing security indicator, the bcm sends a fuel password to the ecm. The ecm disables injector operation to prevent someone from driving away with the car. It works with the only weakness to defeat it with the ignition key if a smart thief wanted any Saturn using Passlock. The security indicator is fool proof and the only visible indicator to determine Passlock status.

Do you know if spark plugs were ever replaced? This may be a strong possibility to prevent spark igniting fuel. Search bills and records. PLease do not ignore this possibility.

If you are comfortable with wiring, you can pull the fuel pump fuse, review pinout labeling on the four or five pin relay, and jumper relay socket terminals 30 and 87; this sends 12v to power the fuel pump immediately, regardless of ignition switch position. Be aware of jumpering incorrectly as 12v sent to ground or ecm may blow a fuse or damage the ecm. When jumpered correctly, you should be able to hear a quiet hissing sound as the fuel pump pressurizes the fuel lines. Depressing the fuel test valve should result in a strong spray of fuel. Two stainless lines over the engine with the test valve capped on the feed line.
Thanks for BCM information.
I have jumped fuel pump relay and it did not turn the pump on. I also found no voltage at term 86 on relay board when first turning key on or cranking.
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Old 06-18-2021, 03:03 AM   #10
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2003 L-Series 3.0L Sedan
Default Re: 2003 l300 no start

There are two fuses, one for power thru f/p relay contacts 30 and 87, the other one a 10A ENGINE CNTL 3 to power the f/p relay. 12v sits on either pin 85 or 86 after the ignition switch is turned on. The ecm sends a ground signal to the f/p relay to energize the relay coil.

At ignition ON time, the fuel pump is energized for 2-3 seconds then power is removed if the engine isn't started. During starting, the ground signal is supplied to again as longs as the engine cranks or fires up. The ecm knows when to supply ground to the f/p relay coil, either as a 2-3 second signal if the engine isn't started or continuously when the crank sensor sends timing signals; the crank sensor supplies precise timing signals only when the engine rotates. allowing the ecm to run the f/p, sync ignition for spark and pulse injectors.
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