P0355 code won't go away.

Discussion in 'General Chevy & GM Tech Questions' started by fishdoktor, Aug 25, 2013.

  1. fishdoktor

    fishdoktor New Member

    Hello everyone. I changed the coil, wire and plug, the cylinder IS firing, checked it with a ignition tester light and is firing perfect. do I have to drive it a while? d
    Disconnected the battery still on. Light doesn't come on while driving, just after each start up. Thanks.
  2. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    Need more info in order to help. what year, what engine, does it come on right after starting, does it go off, if so when. also did you mean P0305 which is cyl 5 missfire? i am not familiar with P0355.
  3. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    X2 on needing more information regarding your vehicle...in the meantime, this info may be of some help to you.


    Ignition Coil E Primary/Secondary Circuit Malfunction

    What does that mean?
    The COP (coil on plug) ignition system is what is used on most modern engines. There is an individual coil for each cylinder that is controlled by the PCM (powertrain control module). It eliminates the need for spark plug wires by putting the coil right above the sparkplug. Two wires are dedicated to each coil. One is a battery feed usually from the power distribution center. The other wire is the coil driver circuit from the PCM. The PCM grounds/ungrounds this circuit to activate or deactivate the coil. The coil driver circuit is monitored by the PCM for faults If an open or a short is detected in the driver circuit for coil #5, a P0355 may set. Also, depending on the vehicle, the PCM may also shut down the fuel injector to the cylinder also.

    Symptoms of a P0355 DTC may include: MIL (Malfunction indicator lamp) illumination; Engine misfire may be present or intermittent

    Potential causes of a P0355 code include: Short to voltage or ground on COP driver circuit; Open on COP driver circuit; Loose connection at coil or broken connector locks; Bad Coil (COP); Faulty Powertrain Control Module

    Possible Solutions
    Is the engine misfiring presently? If not, the problem is likely intermittent. Try wiggle testing the wiring at the #5 coil and along the wiring harness to the PCM. If manipulating the wiring causes the misfire to surface, repair the wiring problem. Check for poor connection at the coil connector. Verify the harness isn't misrouted or chafing on anything. Repair as necessary If the engine is misfiring presently, stop the engine and disconnect the #5 coil wiring connector. Then start the engine and check for a driver signal to the #5 coil. Using a scope will give you a visual pattern to observe, but since most people don't have access to one there's an easier way. Use a Voltmeter in AC Hertz scale and see if there's a Hz reading of between 5 and 20 or so that indicates the driver is working. If there is a Hertz signal, then replace the #5 ignition coil. It's likely bad. If you don't detect any frequency signal from the PCM on the ignition coil driver circuit indicating the PCM is grounding/ungrounding the circuit (or there is no visible pattern on the scope if you have one) then leave the coil disconnected and check for DC voltage on the driver circuit at the ignition coil connector. If there is any significant voltage on that wire then there is a short to voltage somewhere. Find the short and repair it. If there is no voltage on the driver circuit, then turn the ignition off. Disconnect the PCM connector and check the continuity of the driver between the PCM and the coil. If there is no continuity repair the open or short to ground in the circuit. If continuity is present, then check for resistance between ground and the ignition coil connector. There should be infinite resistance. If there isn't, repair the short to ground in the coil driver circuit NOTE: If the ignition coil driver signal wire is not open or shorted to voltage or ground and there is no trigger signal to the coil then suspect a faulty PCM coil driver. Also keep in mind that if the PCM driver is at fault, there may be a wiring problem that caused the PCM failure. It's a good idea to do the above check after PCM replacement to verify there won't be a repeat failure. If you find that the engine isn't misfiring, the coil is being triggered properly but P0355 is continually being reset, there is the possibility that the PCM coil monitoring system may be faulty.
  4. fishdoktor

    fishdoktor New Member

    Sorry, 2000 GMC Sierra 1500 4.8L. It is firing perfect with the test light on it. What is the best route to replace the PCM? Yes the light only comes on 30 seconds after I start it. Going to drive it some more. Also disconnected the Pos side of battery, should I do it again doing the Neg side?
  5. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    Mfleetwood is correct, P0355 is cyl 5 coil CONTROL CIRCUIT fault detected. not a missfire code, however missfire could be present. you don't say but i'm going to assume light goes out till restarted? PCM is located left side in engine compartment, make sure battery is disconnected and you ground yourself to prevent damage to PCM by static electricity. that being said, contrary to popular belief, PCM failure is not very common. people often replace PCMs and not fix the problem or burn out the new one because they did not fix the original problem first!! DTCs are a diagnostic aide only. example, O2 codes will set because of a bad coolant temp sensor, which happens all the time. bad PCM grounds are very common causes of " false" codes. the flow chart Mfleetwood sent is a good place to start. I WOULD NOT REPLACE PCM UNTILL THROUGH TESTING OF CIRCUIT INCLUDING ALL PCM POWER & GROUNDS!!! also check TSBs to see if this this is a known problem. you might be able to swap coil to different cyl & see if code follows. by the way, how is the engine running?
    PS: new stands for NEVER EVER WORKED parts can be bad right out of the box!!

    - - - Updated - - -

    I forgot to mention in my last reply something very important & often overlooked. verify that battery voltage DOES NOT DROP below 10V during cranking! below 10V will "confuse" PCM module resets, false codes etc. around 9V PCM shuts down. this is all general troubleshooting info. the more complete info you can give the better the chance someone can help you fix this.
  6. fishdoktor

    fishdoktor New Member


    Yes I have a cheap scan tool that clears the code after starting the motor. The light will stay out all the while I'm driving till I shut it off and when I restart it after about 30 seconds it's back on. I think I need to put some miles on it, should I drive it with the light on or off?
  7. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    Your welcome. it is very difficult to point you in any different direction without better info from you. you still have not said how the engine is running,are there any other codes,have you done any circuit testing? try this & let me know. remove the connector at the coil, use a small pick or something similar to scrape the terminals clean. tweak them ever so slightly tighter & reconnect. clear the code start it. if the light resets, drive it 30 mins or so, shut it off & clear the code. wait 1 min. restart and see if it sets. do you have a dvom?

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