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98 Bonneville P0300

Model: 98 Bonneville Fault Code: P0300 Posted: 2008-09-03 19:39

Thanks to the other poster I am working on a 98 Bonneville. OBD2 code is P0300 and P 0121 code( bad O2 sensor). Changed O2 sensor and code does not reappear. After new wires and coil packs, I checked the vacuum and fuel pressures which were good. When I pulled the plugs to run a compression check noticed the 1 and 4 cylinder plugs wet. Both are coming off the same coil. Switched coil and wires, pulled 1 plug again an d still wet. My guess is ignition module or ECM. Called local parts store and one is $103 the other $132 and they cannot test either. I only have the code scanner so can not check the rest. Any suggestion on which one it might be? Thought about taking it to a shop but diagnostics would be about as much as one item.

Related fault codes
P0300
Comments (3)
Anonymous 2008-09-03 20:10

My guess is that you can get the ignition module tested at a parts store at no charge and go from there

Anonymous 2008-09-16 17:47

Had the module tested and was bad. Replaced and now P420 code. I think this is from driving with bad module. Plan on driving a few days to burn the fuel in cat and the reset code to see if it reappears.

Anonymous 2008-09-20 20:57

Good news cleared the code and have driven about 100 miles and no codes. Thanks for all the help on this message and other messages.