Hello,

I’m trying to help my neighbor out and get his 2003 L200 running again as he desperately needs transportation. I highly suspect a bad BCM based off my diagnostics and research on the L-Series. I plan on getting a used BCM, but was wondering if the model year on the replacement BCM had to match the car it was going in, or if they were interchangeable between years. Any answers or help is much appreciated!

 

From my experience you will need both a bcm and an airbag module from a same configuration car. I would search for another 2003 or 2004 four cylinder car the VIN is stored in both modules and you can do the 10 minute relearn three times and make everything work. If you only change the bcm you loose airbags. Other people may have had different outcomes but this is what I have experienced.

What does the car do? Crank and fire then die. Or flashing security lights? These break timing chains and bend valves. Have you checked compression if it doesn’t fire at all?

 

Yeah, I’ve read posts of success with and without the airbag module. I think he’d be content with no airbags, he just wants it to run. I found a BCM from a 2004, but with this being a 2003 I wanted to be sure.

The car cranks but doesn’t start. Security light comes on solid, not flashing. There is fuel pressure, and it does sound like there is compression, but I don’t have a compression tester to verify. When plugging in an OBD2 scanner, there is power, but no communication. He said odometer has never counted since he’s owned it, and that it would have intermittent check engine and/or security lights. The last day it ran, he described it going into low power/limp mode, with limited engine rpm and speed, then it shut off and wouldn’t start anymore. He said he didn’t hear any mechanical failure type noises when it died. To me, based on the symptoms it definitely sounds computer related. I did unplug and replug the BCM connectors but still nothing. I also haven’t ruled out a failed ECM.

 

Odometer is the first bcm failure point. As long as the 04 bcm is from a 4 cylinder car it should plug and play. Good luck, the security relearn has to be performed exactly as written. Use a battery charger or jumper cables to a running car. Pull the parking brake up one click to turn off the headlights.

 

Limited power and then death could be a stopped up catalytic converter. I'd disconnect the exhaust from the manifold and see if it starts. As for a compression test, just remove a spark plug and put your finger over the hole while someone cranks it. Kind of a crude way and you can't possibly know how much psi it it, but at least you'll know if there's compression. You need air, spark, fuel and compression in order for an engine to run. You have to find out which one is missing.

 

I think this means the small 'lock' symbol at the bottom of the gauge cluster. If so, the car will NOT start and for my 2003 L200, I have to cycle the key off, than back on just short of 'start'. Wait 10 minutes, the light goes out, cycle the key off than to start, and boom, starts again. Once that light is out, and it starts or turns over and fires and that lock light stays out, than move on to other issues. If it comes right back on though, that means something simple and the old SaturnFans had a thread of adding a resistor to the back of the IGN switch or something? Maybe search here on this forum. I've had that lock light come on while driving occasionally, but doesn't stall the car and the next start it stays out so mine is getting flakey too so if you find a link to that thread, come back and post it for us? Here's a link to the about it...

The ECMs are pretty reliable but do remove the connector(s) and spray with contact cleaner.

 

Yes, on this car there is a lock symbol, but on some models I’ve seen there is the word “SECURITY” on the cluster. I looked at the car again today, I mistakenly said that the security light STAYS on solid, when I meant to say it comes on solid for BULB CHECK, then shuts off. Whoops.

Here are a few more things I discovered: I don’t hear injectors ticking when the engine is turning over. The fuel pump relay is good, but PCM doesn’t trigger the fuel pump relay for 2-3 seconds when key is put in the ON position like it’s supposed to. The fuel pump will run when jumped. I’ve read the BCM controls power to the injectors, and a bad BCM won’t allow them to operate, but can it affect the fuel pump as well? I don’t have a scanner with BCM comm. capability, so I’m trying to work around that. I still should be able to read live data with my basic scanner, but the car won’t communicate.

 

Can you tell us what you did? More than 90% of BCMs replaced are perfectly fine. They get blamed for many things.

 

I have been grinding in this for a few days.
I also have never had a BCM kill a car.
I have one car that the odometer does not work. I know this is BCM and the car runs fine and has been on the road for the last 3 years.
Other than the current LW300 I have all the other no starts have been mechanical engine failures.
My current LW300 had a good engine and a failed ECM- no communication with the ecm. My Snap On scanner would not communicate with the ECM. The Snap On scanner looks at the ECM first.
I cranked the engine and knew it had compression. Granted I do this for a living and I am old. 69 and counting.
I scanned for all the other computers and behold all the other computers reported no communication with the ECM.
One of the health checks I have learned to do is to see what computers respond and “which one is missing”?

FYI, the new Fords I work on have 24 computers so you have to pay attention.

FYI! code readers only read OBD2 emission code data and are no help diagnosing cars that do not run. However they can point you in the right direction if there is no communication.
A flashing engine light can help pinpoint the misfiring cylinder. It is shut down to keep from melting the catalytic converter. The cylinder usually is fueled but not fired due to low compression or no spark. Excess fuel creates extreme heat that the catalytic converter cannot deal with so it shuts down the injector to prevent meltdown.

I would do a mechanical inspection on the engine before proceeding. The L61 engine is known for timing chain failure at early mileages due to poor maintenance intervals or improper oil choices. Quaker State and Pennzoil are satisfactory if changed when the color changes. You cannot go by mileages with this oil, it quits working when it changes color, it is done!
I have done numerous engine repairs on the L61 engine all due to timing chain failures. I got lucky on one and the chain only jumped and did not bend the valves. All the other ones dumped the chain and bent a majority of the valves. A few have run out of oil and ventilated the block. Let’s say I have scrapped a few L series cars. I am up to double digits on L series cars. I have grandchildren in a couple right now plus my big block wagon plus an L61 Oldsmobile..

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So, an update, the car finally started! In the process of trying to further diagnose it, the ignition lock cylinder got stuck and was not allowing the key to fully enter, then it accepted the key but wouldn’t turn. I determined the key was just too worn out as my neighbor had already replaced the cylinder but not his original Saturn key. We took the key to Home Depot, and had a replacement cut. The machine scans the key and cuts it, and it came out perfect for only a few dollars. Well, the lock cylinder was still refusing to turn. As a last resort before drilling it out, I flooded it with WD-40 and used pliers for leverage, and finally it turned. Just out of curiosity, I turned the key all the way to start and the car cranked and fired up like nothing ever happened! No security light or anything, kind of strange. We were both in total shock. The engine sounds quiet and healthy, but it’ll need some maintenance before going back on the road.

Thanks everyone for your help and advice!