Document ID# 546823
2000 Chevrolet Chevy C Silverado - 2WD
--------------------------------------------------------------------------------
DTC P0300 Engine Misfire Detected
Circuit Description
The crankshaft position (CKP) sensor is mounted through the side of the
engine block at the rear of bank 2 above the starter assembly. The CKP
sensor works in conjunction with a 24X reluctor wheel on the crankshaft. The
reluctor wheel is inside the engine immediately in front of the rear main
bearing. The powertrain control module (PCM) provides a 12 volt power supply
to the CKP sensor as well as a ground and a signal circuit.
A misfire causes a change in crankshaft speed. The PCM times the interval
between each pulse and compares each new time interval with the previous one
in order to determine when an excessive change in crankshaft speed has
occurred. You can expect a certain amount of acceleration or deceleration
between each firing stroke, but if the crankshaft speed changes are more
than an expected amount, the PCM interprets this as a misfire.
The PCM uses the CKP sensor for misfire detection and to control spark and
fueling. As the crankshaft rotates, the reluctor wheel teeth interrupt a
magnetic field produced by a magnet within the sensor. The sensors internal
circuitry detects this and produces a signal which the PCM reads. The PCM
uses this 24X signal in combination with the camshaft position (CMP) sensor
1X signal in order to accurately determine crankshaft position. The PCM also
calculates a 4X signal from this information. The PCM uses the 4X signal for
internal calculations. The 4X signal also provides a tach signal for any
device which requires one.
Observe that as long as the PCM receives the CKP sensor 24X signal, the
engine will start. The PCM can determine top dead center for all cylinders
by using the CKP sensor 24X signal alone. The CMP sensor 1X signal is used
by the PCM to determine if the cylinder at top dead center is on the firing
stroke or the exhaust stroke. The system attempts synchronization and looks
for an increase in engine speed indicating the engine started. If the PCM
does not detect an increase in engine speed, the PCM assumes it incorrectly
synchronized to the exhaust stroke and re-syncs to the opposite cam
position. A slightly longer cranking time may be a symptom of this
condition.
Conditions for Running the DTC
• No active mass air flow (MAF) DTCs
• No active engine coolant temperature (ECT) DTCs
• No active throttle position (TP) DTCs
• No active crankshaft position (CKP) sensor DTCs
• No active camshaft position (CMP) sensor DTCs
• No active vehicle speed sensor (VSS) DTCs
• The engine speed is between 375 RPM and 5,001 RPM for automatic
transmission.
• The engine speed is between 450 RPM and 5,001 RPM for manual
transmission.
• The ignition voltage is between 10 volts and 18 volts.
• The ECT is between -7°C (19°F) and +130°C (+266°F).
• Fuel level more than 10 percent
• The TP sensor angle is steady within 1 percent.
• The antilock brake system (ABS) and traction control systems are
not active.
• The transmission is not changing gears.
• The secondary air injection (AIR) diagnostic test is not in
progress (RPO NC1 only)
• The A/C clutch is not changing states.
• The PCM is not in fuel shut-off or decel fuel cut-off mode.
• The ABS signal is not exceeding rough road thresholds.
Conditions for Setting the DTC
• The PCM determines that an emission type misfire is present.
• The PCM determines that a catalyst damaging misfire is present.
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL) under the following
conditions:
• The PCM illuminates the MIL on the second consecutive ignition
cycle that the diagnostic runs and fails, if the diagnostic fails under the
same conditions such as load, RPM, temperature, etc. as the previous
ignition cycle that the test ran and failed.
• The first time the diagnostic fails, the PCM records the
operating conditions in Failure Records.
• The PCM determines the percent of misfire over a 1,000
revolution period is high enough to cause excessive tail pipe emissions. The
PCM illuminates the MIL the next consecutive ignition cycle that the
diagnostic runs and fails, if the diagnostic fails under the same conditions
such as load, RPM, temperature, etc. as the previous ignition cycle that the
test ran and failed. Or
• The PCM flashes the MIL when the diagnostic runs and fails a
catalyst damaging misfire.
Conditions for Clearing the MIL/DTC
Important: If the last failure was during a non-typical driving condition,
the MIL may remain ON longer than the three ignition cycles. Review the
Freeze Frame or Failure Records for the last failure conditions.
• The PCM turns the MIL OFF after three consecutive ignition
cycles that the diagnostic runs and does not fail within the same conditions
that the DTC last failed.
• A History DTC clears after forty consecutive warm-up cycles, if
this or any other emission related diagnostic does not report any failures.
• A last test failed clears when the diagnostic runs and does not
fail.
• Use a scan tool in order to clear the MIL/DTC.
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before
servicing the PCM. Inspect the PCM connector gaskets when diagnosing or
replacing the PCM. Ensure that the gaskets are installed correctly. The
gaskets prevent water intrusion into the PCM.
• Running the vehicle out of fuel causes sufficient misfire to set
DTC P0300. A vehicle that is out of fuel may have fuel level DTCs also set.
• Water contamination in the fuel system can cause a single
cylinder to misfire as well as cause a random misfire. If there is a misfire
in Cylinder #7 it is possible that water has collected in the fuel rail.
Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
• If there is a misfire detected in Cylinder #4or #6 it is
possible that the fuel pressure regulator diaphragm has ruptured, causing
fuel to be drawn in through the regulator vacuum line. Remove the vacuum
line and inspect for fuel contamination.
• A restricted fuel filter can cause sufficient misfire to set DTC
P0300. Refer to Fuel System Diagnosis .
• Excessive vibration from sources other than the engine could
cause a misfire DTC. The following are possible sources of vibration:
- Variable thickness brake rotor
- Drive shaft not balanced
- Certain rough road conditions
• Observe, if more then one cylinder is misfiring, the scan tool
may only display one cylinder misfiring. This will not be apparent until the
repair is completed. Also, if an ignition coil ground circuit is open for
one side of the engine, the scan tool may only display 2 or 3 cylinders
misfiring. Inspect the ground circuit for the ignition coil on the cylinder
bank of the engine that has more then one cylinder misfiring.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
b.. Wetting down the secondary ignition system with water from a spray
bottle may help locate damaged or deteriorated components. Look and listen
for arcing or misfiring as you apply the water.
If the Misfire Current counters are incrementing and there is no apparent
misfire, an erratic CKP sensor signal could be the cause. Perform the
diagnostic table for DTC P0335 first if this condition is suspected.
If a misfire is present and you suspect a fuel control problem, force the
fuel system into Open Loop using the scan tool and allow the engine to run
for a few minutes. If this eliminates the misfire, refer to any fuel control
related DTCs which are set. If no other DTCs are set, refer to the Engine
Scan Tool Data List.
A misfire may not be apparent at idle. The misfire may only occur above
idle under a load. Road test the vehicle and monitor the misfire current
counters.
If more than one cylinder is misfiring, the misfire current counters may
only increment for one cylinder. Example: Cylinders 1 and 8 are both
misfiring, yet only cylinder 8 increments on the misfire current counter.
If one of the injector fuses is open, only two or three misfire current
counters may increment for the corresponding side of the engine.
d.. The cylinder with the more significant misfire may cause another
cylinder counter to increment only by a small amount.
j.. If the engine misfire moves with the spark plug, this is good
indication that you should replace the spark plug.
l.. An engine mechanical problem can cause a spark plug to gas foul.
Inspect for loose rockers, collapsed lifters, or worn camshaft lobes.
q.. If the customer concern is the MIL flashing, this indicates that a
Catalyst Misfire has occurred. Drive the vehicle in the conditions to run
the catalyst diagnostic.
DTC P0300 - Engine Misfire Detected Step
Action
Value(s)
Yes
No
1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check
2
Important
a.. You must perform the CKP System Variation Learn Procedure before
proceeding with this diagnostic table. Refer to CKP System Variation Learn
Procedure .
b.. If any DTCs are set, refer to those DTCs before proceeding with
this diagnostic.
c.. If any abnormal engine mechanical noise can be heard, refer to
Base Engine Misfire Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
1.. Install the scan tool.
2.. Idle the engine.
3.. Monitor all the Misfire Current counters on the misfire data
list using a scan tool. There are a total of 8 counters, One counter per
cylinder.
Are any of the Misfire Current counters incrementing?
--
Go to Step 4
Go to Step 3
3
1.. Turn ON the ignition, with the engine OFF.
2.. Review the Freeze Frame and Failure Records data for this DTC
and observe the parameters.
3.. Turn OFF the ignition for 15 seconds.
4.. Start the engine.
5.. Operate the vehicle within the conditions required for this
diagnostic to run, and as close to the conditions recorded in the Freeze
Frame and Failure Records as possible. Special operating conditions that you
need to meet before the PCM will run this diagnostic, where applicable, are
listed in Conditions for Running the DTC.
6.. Select the Diagnostic Trouble Code (DTC) option, the Specific
DTC option, and then enter the DTC number using the scan tool.
Does the scan tool indicate that this diagnostic failed this ignition?
--
Go to Step 4
Go to Diagnostic Aids
4
Is only one misfire counter incrementing?
--
Go to Step 6
Go to Step 5
5
Visually and physically inspect the following items:
a.. Vacuum hoses for splits, kinks, and proper connection -- Refer
to Emission Hose Routing Diagram .
b.. Throttle body and intake manifold for vacuum leaks
c.. Crankcase ventilation valve and/or system for vacuum leaks --
Refer to Crankcase Ventilation System Description .
d.. PCM grounds for being clean and secure -- Refer to Ground
Distribution Schematics in Wiring Systems.
e.. Inspect the ignition coil ground circuit for an open on the
cylinders that are showing misfires. An open ground causes all four Ignition
Coils to be inoperative. The Misfire current counters only displays 2-3
cylinders misfiring, not all four cylinders.
f.. Inspect that all injector harness connectors that are connected
to the proper injector
g.. Check the injector and ignition control fuses for being open. If
you find an open fuse, locate and repair the shorted circuit. Refer to
Wiring Repairs in Wiring Systems.
h.. Test for incorrect fuel pressure or restricted fuel flow. Refer
to Fuel System Diagnosis .
i.. Inspect for a restricted exhaust. Refer to Restricted Exhaust in
Engine Exhaust.
j.. Test for fuel contamination. Refer to
Alcohol/Contaminants-in-Fuel Diagnosis .
k.. If an abnormal engine mechanical noise is heard, refer to Base
Engine Misfire Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
Did any of the above checks isolate a condition requiring a repair?
--
Go to Step 17
Go to Step 6
6
Important
Before disconnecting the injector harness, refer to Fuel Rail Assembly
Replacement . There is a special procedure for disconnecting the fuel
injector harness connectors.
1.. Turn OFF the ignition.
2.. Disconnect the injector that corresponds to the Misfire Current
counters that were incrementing.
3.. Connect the injector J 34730-405 test lamp to the injector
electrical connector.
4.. Idle the engine.
Is the injector test lamp flashing?
--
Go to Step 7
Go to DTC P0200 Injector Control Circuit
7
1.. Turn OFF the ignition.
2.. Reconnect the injector harness electrical connector.
3.. Disconnect the ignition wires from the spark plug that
corresponds to the Misfire Current counters that were incrementing. Refer to
Spark Plug Wire Harness Replacement in Engine Electrical.
4.. Install the J 26792 spark tester to a ground.
5.. Start the engine.
Does the spark jump the tester gap and is the spark consistent?
--
Go to Step 9
Go to Step 8
8
1.. Remove the ignition wire for the cylinder that is misfiring. Refer
to Spark Plug Wire Harness Replacement in Engine Electrical.
2.. Measure the resistance of the ignition wire using the DMM.
Is the ignition wire resistance less than the specified resistance?
700 ohms
Go to Electronic Ignition (EI) System Diagnosis
Go to Step 16
9
Remove the spark plugs from the cylinder that indicated a misfire.
Refer to Spark Plug Replacement in Engine Electrical.
Does the spark plug appear to be OK?
--
Go to Step 10
Go to Step 11
10
Important
If the Injector Coil Test Procedure checks to be OK, refer to Base
Engine Misfire Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
1.. Swap the suspected spark plug with another cylinder that is
operating properly. Refer to Spark Plug Replacement in Engine Electrical.
2.. Operate the vehicle under the same conditions that the misfire
occurred.
Did the misfire move with the spark plug?
--
Go to Step 15
Go to Fuel Injector Coil Test - Engine Coolant Temperature (ECT)
Between 10-35 Degrees C (50-95 Degrees F)
11
Are the spark plugs oil or coolant fouled?
--
Go to Base Engine Misfire Diagnosis in Engine Mechanical 4.8L, 5.3L,
6.0L
Go to Step 12
12
Important
If the fuel system checks to be OK, refer to Base Engine Misfire
Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
Are the spark plugs gas fouled?
--
Go to Fuel System Diagnosis
Go to Step 13
13
Important
If the Injector Coil Test Procedure checks to be OK, refer to Base
Engine Misfire Diagnosis in Engine Mechanical 4.8L, 5.3L, 6.0L.
Do the spark plugs show any signs of being cracked, worn, or
improperly gapped?
--
Go to Step 14
Go to Fuel Injector Coil Test - Engine Coolant Temperature (ECT)
Outside 10-35 Degrees C (50-95 Degrees F)
14
Replace or re-gap spark plugs. Refer to Spark Plug Replacement in
Engine Electrical. If an improper gap is found, be sure to re-gap spark
plugs using a wire type gauge.
Is the action complete?
--
Go to Step 17
--
15
Replace the faulty spark plugs. Refer to Spark Plug Wire Harness
Replacement in Engine Electrical.
Is the action complete?
--
Go to Step 17
--
16
Replace the faulty ignition wires. Refer to Spark Plug Wire Harness
Replacement in Engine Electrical.
Is the action complete?
--
Go to Step 17
--
17
If the customers concern that the MIL was flashing, were any Catalyst
DTC's set?
--
Go to DTC P0420 Catalyst System Low Efficiency Bank 1 or DTC P0430
Catalyst System Low Efficiency Bank 2
Go to Step 18
18
1.. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC
Information option using the scan tool.
2.. Idle the engine at the normal operating temperature.
3.. Select the Diagnostic Trouble Code (DTC) option and the Specific
DTC option, then enter the DTC number using the scan tool.
4.. Operate the vehicle within the Conditions for Running the DTC as
specified in the supporting text, if applicable.
Does the scan tool indicate that this test ran and passed?
--
Go to Step 19
Go to Step 2
19
Select the Capture Info option and the Review Info option using the
scan tool.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to the applicable DTC table
System OK
--------------------------------------------------------------------------------
Document ID# 546823
2000 Chevrolet Chevy C Silverado - 2WD
Info - Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due
to Installation of Alarm Systems #02-06-05-004b - (02/14/2006)
Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or
P0430 #06-06-04-046 - (09/12/2006)
Due to various factors, the fuel injectors may become restricted. Extensive
testing has demonstrated that fuel related issues are the cause of clogged
injectors. At this point, no specific fuel, fuel constituent, or engine
condition has been identified as causing the restriction. The restriction
causes the engine to operate at a lean air fuel ratio. This may either
trigger the MIL to illuminate or the engine to develop various driveability
symptoms.
Correction
Fuel injector restrictions, deposits can be cleaned on the vehicle using the
following procedure. Under NO circumstances should this procedure be
modified, changed or shortened. As a long term solution, and to prevent
reoccurrence, customers should be encouraged to use Top Tier Detergent
Gasoline . For further information on Top Tier detergent gasoline and fuel
retailers, please refer to the following Corporate Bulletin Numbers:
• 04-06-04-047G (U.S. Only)
paul
"DRIO" wrote in message
>I scanned the truck and get a DTC P0300 Random Misfires. So far I changed
> the sparkplugs, Bank2 Sensor 2 oxygen sensor also had a DTC P0161 code. I
> also changed the fuel filter. I also added a can of fuel cleane and took
> it
> on a long ride. No difference. I get the misfire once the truck has warmed
> up and is working hard like going up a slight incline or pulling the fifth
> wheel trailer. Any suggestions would be appreciated.
>
> >> Stay informed about: 2000 2500 Sierra 6 .0L Random misfires 
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