I have a big problem with my son's 2004 Neon. While driving, the #3 spark plug blew out. Installed an insert, changed plugs, wires and ignition coils since it was missing on #3, but now the car burns a lot of fuel--like a tank in 20 miles--gas is pooling under tailpipe. Changed Upstream O2 sensor and reset codes--came up with P0203 only. Listened to each injector with a screwdriver to the ear--1, 2, and 4 are clicking, 3 is not. Swapped #3 injector with #2 injector and still came up with P0203 only. Checked injector resistance--all 4 injectors are 12 ohms. Voltage on 1, 2, and 4 injector connector is about 1 volt--#3 injector is 13 V. Continuity check shows that #3 injector connector is short to ground while others are not. Replaced wire from injector connector to PCM, still have code P0203 as well as the same continuity and voltage readings. It looks to me that it must be the PCM since the injectors and wiring have been ruled out--any thoughts?

 

According to the FSM, you should also check the ASD relay output circuit.

Might need to jump the ASD relay in place of using the DRBIII?

After the ASD circuit, the PCM is the only thing left I think.

 

Thanks, I will check that out and let you know how it goes. I ordered a new PCM, but wont be able to put it in until next week. I am hoping that does the trick--if not, I will need some advice.

 

I changed out the PCM and it fixed the initial problem. Now there is no spark on 2 and 3--showing code P2305 which is #2 coil secondary circuit insufficient ionization. The coil checks out ok as far as resistance--it is a new one. I dont have any diagnostic tools to check the ASD relay, but it was the same p/n as the horn relay so I swapped them--no help. The car seems to be running fine, but only on 2 cylinders. Any advice on what to check?