98 Buick Lesabre p0203 p0303

[danlaw]

I bought a 98 Buick LeSabre Limited about 2 weeks ago from the original owner it ran great with 124,000 miles no problems very clean. Now suddenly i get a miss and get 2 codes P0303 and P0203. i changed the plugs and wires because they looked to be originals. The Injector was inexpensive so i went and replaced that, it didn't help anything. After doing all that i went and listened with a scope and screw driver on the injector i noticed its not firing, so i disconnected the injector and used that cyc 3 plug on my cyc 5 and it wouldn't let that injector fire either. so i know that's its not getting the signal to fire. the cyc 3 plug is getting voltage but it doesn't go up or down with it running. I've read conflicting stuff saying it could be the cam position sensor or the PCM. I'm at a road block and not sure what to do, I'd rather not keeping changing stuff till i finally figure it out so i found this nice site and would appreciate any ideas on my problem. thanks to any and all who can help me.


got this from a servicing GMs 3800 site "If an injector reads good, use a noid light to check for an injector pulse from the PCM injector driver circuit. No pulse? The problem could be a bad injector driver circuit in the PCM, or no input from the camshaft position sensor (CMP), which the PCM uses to fire the injectors. The CMP sensor is mounted on the front timing cover. "


please help not sure what to do. also noticed a low whistle that gets louder till the gear changes then gets quieter. might be something totally separate.

[maxwedge]

Welcome to AF, do you have pulse at the injector connector, not clear in your post, if not check the resistance of all the injectors, a bad one can pull down the current to another one.

[danlaw]

when i mean i tested it checked the voltage on the plug to cyc 3 and it stayed constant as where cyc plus was jumping up and down every second.

[danlaw]

when i meant when i said tested it was i checked the voltage on the plug to cyc 3 and it stayed constant as where the cyc 1 plug was jumping up and down every second.

[maxwedge]

Is this with a test lite, voltmeter or noid lite?

[stuzman]

Originally Posted by danlaw

I bought a 98 Buick LeSabre Limited about 2 weeks ago from the original owner it ran great with 124,000 miles no problems very clean. Now suddenly i get a miss and get 2 codes P0303 and P0203. i changed the plugs and wires because they looked to be originals. The Injector was inexpensive so i went and replaced that, it didn't help anything. After doing all that i went and listened with a scope and screw driver on the injector i noticed its not firing, so i disconnected the injector and used that cyc 3 plug on my cyc 5 and it wouldn't let that injector fire either. so i know that's its not getting the signal to fire. the cyc 3 plug is getting voltage but it doesn't go up or down with it running. I've read conflicting stuff saying it could be the cam position sensor or the PCM. I'm at a road block and not sure what to do, I'd rather not keeping changing stuff till i finally figure it out so i found this nice site and would appreciate any ideas on my problem. thanks to any and all who can help me.


got this from a servicing GMs 3800 site "If an injector reads good, use a noid light to check for an injector pulse from the PCM injector driver circuit. No pulse? The problem could be a bad injector driver circuit in the PCM, or no input from the camshaft position sensor (CMP), which the PCM uses to fire the injectors. The CMP sensor is mounted on the front timing cover. "


please help not sure what to do. also noticed a low whistle that gets louder till the gear changes then gets quieter. might be something totally separate.

It sounds like you checked the supply volts and it's there. If you don't have the pulse at the other side, two things it could be. Either the driver in the PCM is out or you have a open connection on the side of the driver. The CMP sensor is used to synchronize the injector firing. The injectors will still fire without the CMP pulses.

[danlaw]

when i went to check the PCM the container it was in had moisture inside of it. so i went and vacuumed it out and cleaned everything and reinstalled it and it worked beautifully.

wish i checked that 1st, thx for all the help again!