Question about GMC Cars & Trucks
It could be bad spark plugs, plug caps/wires, coil, fuel injector.. you will have to find out what is causing the misfire and repair. this code tells you that the misfire is not isolated to a single cylinder.
Posted on Mar 28, 2015
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Posted on Jan 02, 2017
SOURCE: multiple cylinder misfire
There could be a couple of reasons for this. If you are getting multiple misfires then usually it has something to due with the plugs going bad. It also depends on how many miles you have on the plugs and the wires. The other problem could be with the ignition coils or the ignition module.
Posted on Apr 10, 2010
Look at the spark plug, if looks ok then that's not the problem.with spark plug out check cylinder compression if good then check fuel injector, reinstall spark plug, start engine and listen for clicking noise at fuel injector, if none bad injector replace.
Posted on May 14, 2010
SOURCE: I changed the plugs and
if its a multiple missfire then i would suspect your fuel pressure is dropping or your regulator has failed and is sucking too much fuel causing the computer to overcompensate, these engines are also known for intake leaks
Posted on Mar 28, 2011
If spark plugs and wires are done and it doesn't have a dead miss under load, usually it is the crank sensor acting up. It is a colon tab in all repair manuals
Posted on Mar 02, 2012
SOURCE: code 0300 ,0303,0351,and2302
DTC P0300 - RandomMultiple Cylinder Misfire Detected
Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present
A code P0300 may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
DTC P0351 - Ignition Coil A Primary/Secondary Circuit Malfunction
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 number 1, a P0351 may set. Also, depending on the vehicle, the PCM may also shut down the fuel injector to the cylinder also.
Symptoms of a P0351 DTC may include:
MIL (Malfunction indicator lamp) illumination
Engine misfire may be present or intermittent
Potential causes of a P0351 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
Is the engine misfiring presently? If not, the problem is likely intermittent. Try wiggle testing the wiring at the #1 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 #1 coil wiring connector. Then start the engine and check for a driver signal to the #1 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 #1 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 P0351 is continually being reset, there is the possibility that the PCM coil monitoring system may be faulty.
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Posted on Jun 29, 2012
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