P0300 code and flashing CEL
Thread Starter
Team Owner
Joined: Nov 2001
Posts: 45,000
Likes: 585
P0300 code and flashing CEL
04 with 22k miles
I was enjoying some cool weather and out on a back road, at about 25 I stomped the gas, after the shift from 1st to 2nd (it's an auto) the CEL began blinking and I lost significant power. I checked the codes and had a Current P0300 and no History. I did NOT reset it. I slowed down and after a short while the light went out. I hit it again and it did not repeat. I checked the codes and the P0300 was GONE. The only difference between the two stabs of the throttle was that the traction control was ON the first time and OFF the second time. Any explanations are welcome.
I was enjoying some cool weather and out on a back road, at about 25 I stomped the gas, after the shift from 1st to 2nd (it's an auto) the CEL began blinking and I lost significant power. I checked the codes and had a Current P0300 and no History. I did NOT reset it. I slowed down and after a short while the light went out. I hit it again and it did not repeat. I checked the codes and the P0300 was GONE. The only difference between the two stabs of the throttle was that the traction control was ON the first time and OFF the second time. Any explanations are welcome.
Drifting
Joined: Jul 2007
Posts: 1,365
Likes: 1,818
I have no first hand experience with this but from the manual, there is lots to look at.
DTC P0300
System Description
The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.
Conditions for Running the DTC
DTC P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0335, P0336, P0341, P0342, P0343, P0410, P0500, P0502, P0503, P1114, P1115, P1120, and P1220 are not set.
The engine speed is between 425-3,000 RPM.
The ignition voltage is between 10-18 volts.
The engine coolant temperature (ECT) is between -7 and +130°C (19-266°F).
The fuel level is more than 10 percent.
The throttle angle is steady within 1 percent.
The antilock brake system (ABS) and the traction control system are not active.
The transmission is not changing gears.
The A/C clutch is not changing states.
The PCM is not in fuel shut-off or decel fuel cut-off mode.
The PCM is not receiving a rough road signal.
Conditions for Setting the DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:
Variable thickness brake rotors--Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.
Drive shaft not balanced--Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.
Worn or damaged accessory drive belt--Refer to Base Engine Misfire without Internal Engine Noises in Engine Mechanical.
There may be more or less cylinders actually misfiring than indicated by the scan tool.
Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.
If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
If the actual CKP variation values are not within the learned values, the misfire counters may increment.
DTC P0135 or P0155 can be set because of a misfire.
Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to CKP System Variation Learn Procedure .
Start the engine.
Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
Monitor all of the misfire counters with the scan tool.
Are any of the current misfire counters incrementing?
--
Go to Step 3
Go to Diagnostic Aids
3
Are any DTCs other than P0300, P0135 or P0155 set?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 4
4
Can any abnormal engine noise be heard?
--
Go to Base Engine Misfire without Internal Engine Noises
Go to Step 5
5
Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are below the specified value?
200 mV
Go to DTC P0131 or P0151
Go to Step 6
6
Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are fixed above the specified value?
900 mV
Go to DTC P0132 or P0152
Go to Step 7
7
Inspect the following components:
The vacuum hoses and seals for splits, restrictions, and improper connection--Refer to Emission Hose Routing Diagram .
The throttle body and intake manifold for vacuum leaks
The crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.
The PCM grounds for corrosion and loose connections--Refer to Ground Distribution Schematics in Wiring Systems.
The exhaust system for restrictions--Refer to Restricted Exhaust in Engine Exhaust.
The fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Did you find and correct the condition?
--
Go to Step 20
Go to Step 8
8
Turn OFF the ignition.
Disconnect the spark plug wire from the spark plug that corresponds to the Misfire Current counters that were incrementing. Refer to Spark Plug Wire Replacement .
Install the J 26792 Spark Tester to a good ground.
Start the engine.
Does the spark jump the tester gap, and is the spark consistent?
--
Go to Step 10
Go to Step 9
9
Remove the spark plug wire for the affected cylinder. Refer to Spark Plug Wire Replacement .
Inspect the spark plug wire. Refer to Spark Plug Wire Inspection .
Measure the resistance of the spark plug wire with a DMM.
Is the spark plug wire resistance less than the specified value?
700 ohms
Go to Electronic Ignition (EI) System Diagnosis
Go to Step 19
10
Remove the spark plug from the cylinders that indicated a misfire.
Inspect the spark plug. Refer to Spark Plug Inspection .
Does the spark plug appear to be OK?
--
Go to Step 11
Go to Step 12
11
Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement .
Operate the vehicle under the same conditions that the misfire occurred.
Did the misfire move with the spark plug?
--
Go to Step 18
Go to Step 15
12
Are the spark plugs oil or coolant fouled?
--
Go to Base Engine Misfire without Internal Engine Noises
Go to Step 13
13
Are the spark plugs gas fouled?
--
Go to Step 16
Go to Step 14
14
Do the spark plugs show any signs of being cracked, worn, or improperly gapped?
--
Go to Step 17
Go to Step 15
15
Perform the fuel injector coil test. Refer to Fuel Injector Coil Test .
Did you find and correct the condition?
--
Go to Step 20
Go to Base Engine Misfire without Internal Engine Noises
16
Perform the fuel system diagnosis. Refer to Fuel System Diagnosis .
Did you find and correct the condition?
--
Go to Step 20
Go to Base Engine Misfire without Internal Engine Noises
17
Replace or gap the spark plug. Refer to Spark Plug Replacement . If an improper gap is found, be sure to gap the spark plugs using a wire type gage.
Did you complete the replacement?
--
Go to Step 20
--
18
Replace the faulty spark plug. Refer to Spark Plug Replacement .
Did you complete the replacement?
--
Go to Step 20
--
19
Replace the faulty spark plug wire. Refer to Spark Plug Wire Replacement .
Did you complete the replacement?
--
Go to Step 20
--
20
Was the customer concern the MIL flashing?
--
Go to Step 21
Go to Step 22
21
Operate the vehicle at the specified value for 4 minutes.
Operate the vehicle within the Conditions for Running the DTC P0420 or P0430 as specified in the supporting text. Refer to DTC P0420 or P0430 .
Does the DTC run and pass?
2500 RPM
Go to Step 22
Go to DTC P0420 or P0430
22
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 23
23
Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
DTC P0300
System Description
The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.
Conditions for Running the DTC
DTC P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0335, P0336, P0341, P0342, P0343, P0410, P0500, P0502, P0503, P1114, P1115, P1120, and P1220 are not set.
The engine speed is between 425-3,000 RPM.
The ignition voltage is between 10-18 volts.
The engine coolant temperature (ECT) is between -7 and +130°C (19-266°F).
The fuel level is more than 10 percent.
The throttle angle is steady within 1 percent.
The antilock brake system (ABS) and the traction control system are not active.
The transmission is not changing gears.
The A/C clutch is not changing states.
The PCM is not in fuel shut-off or decel fuel cut-off mode.
The PCM is not receiving a rough road signal.
Conditions for Setting the DTC
The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:
Variable thickness brake rotors--Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.
Drive shaft not balanced--Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.
Worn or damaged accessory drive belt--Refer to Base Engine Misfire without Internal Engine Noises in Engine Mechanical.
There may be more or less cylinders actually misfiring than indicated by the scan tool.
Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.
If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
If the actual CKP variation values are not within the learned values, the misfire counters may increment.
DTC P0135 or P0155 can be set because of a misfire.
Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to CKP System Variation Learn Procedure .
Start the engine.
Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
Monitor all of the misfire counters with the scan tool.
Are any of the current misfire counters incrementing?
--
Go to Step 3
Go to Diagnostic Aids
3
Are any DTCs other than P0300, P0135 or P0155 set?
--
Go to Diagnostic Trouble Code (DTC) List
Go to Step 4
4
Can any abnormal engine noise be heard?
--
Go to Base Engine Misfire without Internal Engine Noises
Go to Step 5
5
Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are below the specified value?
200 mV
Go to DTC P0131 or P0151
Go to Step 6
6
Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are fixed above the specified value?
900 mV
Go to DTC P0132 or P0152
Go to Step 7
7
Inspect the following components:
The vacuum hoses and seals for splits, restrictions, and improper connection--Refer to Emission Hose Routing Diagram .
The throttle body and intake manifold for vacuum leaks
The crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.
The PCM grounds for corrosion and loose connections--Refer to Ground Distribution Schematics in Wiring Systems.
The exhaust system for restrictions--Refer to Restricted Exhaust in Engine Exhaust.
The fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Did you find and correct the condition?
--
Go to Step 20
Go to Step 8
8
Turn OFF the ignition.
Disconnect the spark plug wire from the spark plug that corresponds to the Misfire Current counters that were incrementing. Refer to Spark Plug Wire Replacement .
Install the J 26792 Spark Tester to a good ground.
Start the engine.
Does the spark jump the tester gap, and is the spark consistent?
--
Go to Step 10
Go to Step 9
9
Remove the spark plug wire for the affected cylinder. Refer to Spark Plug Wire Replacement .
Inspect the spark plug wire. Refer to Spark Plug Wire Inspection .
Measure the resistance of the spark plug wire with a DMM.
Is the spark plug wire resistance less than the specified value?
700 ohms
Go to Electronic Ignition (EI) System Diagnosis
Go to Step 19
10
Remove the spark plug from the cylinders that indicated a misfire.
Inspect the spark plug. Refer to Spark Plug Inspection .
Does the spark plug appear to be OK?
--
Go to Step 11
Go to Step 12
11
Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement .
Operate the vehicle under the same conditions that the misfire occurred.
Did the misfire move with the spark plug?
--
Go to Step 18
Go to Step 15
12
Are the spark plugs oil or coolant fouled?
--
Go to Base Engine Misfire without Internal Engine Noises
Go to Step 13
13
Are the spark plugs gas fouled?
--
Go to Step 16
Go to Step 14
14
Do the spark plugs show any signs of being cracked, worn, or improperly gapped?
--
Go to Step 17
Go to Step 15
15
Perform the fuel injector coil test. Refer to Fuel Injector Coil Test .
Did you find and correct the condition?
--
Go to Step 20
Go to Base Engine Misfire without Internal Engine Noises
16
Perform the fuel system diagnosis. Refer to Fuel System Diagnosis .
Did you find and correct the condition?
--
Go to Step 20
Go to Base Engine Misfire without Internal Engine Noises
17
Replace or gap the spark plug. Refer to Spark Plug Replacement . If an improper gap is found, be sure to gap the spark plugs using a wire type gage.
Did you complete the replacement?
--
Go to Step 20
--
18
Replace the faulty spark plug. Refer to Spark Plug Replacement .
Did you complete the replacement?
--
Go to Step 20
--
19
Replace the faulty spark plug wire. Refer to Spark Plug Wire Replacement .
Did you complete the replacement?
--
Go to Step 20
--
20
Was the customer concern the MIL flashing?
--
Go to Step 21
Go to Step 22
21
Operate the vehicle at the specified value for 4 minutes.
Operate the vehicle within the Conditions for Running the DTC P0420 or P0430 as specified in the supporting text. Refer to DTC P0420 or P0430 .
Does the DTC run and pass?
2500 RPM
Go to Step 22
Go to DTC P0420 or P0430
22
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 23
23
Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
There are 2 type of P030X, codes.
1) The generic P0300-random cylinder misfire.
2) The P030X wheer X is a number from 1-8 designating the cylinder with the misfire.
Unfortunately, the DIC code reader will not show any of the P0301-8 codes, only the more Generic P0300 even if it's only 1 cylinder having an issue.
I have an old Actron code reader that will show the P030X codes as well as the I/M monitors that the DIC shows none of. The 1st thing I would check is to see if you have a specific cylinder code still stored.
1) The generic P0300-random cylinder misfire.
2) The P030X wheer X is a number from 1-8 designating the cylinder with the misfire.
Unfortunately, the DIC code reader will not show any of the P0301-8 codes, only the more Generic P0300 even if it's only 1 cylinder having an issue.
I have an old Actron code reader that will show the P030X codes as well as the I/M monitors that the DIC shows none of. The 1st thing I would check is to see if you have a specific cylinder code still stored.
Thread Starter
Team Owner
Joined: Nov 2001
Posts: 45,000
Likes: 585
There are 2 type of P030X, codes.
1) The generic P0300-random cylinder misfire.
2) The P030X wheer X is a number from 1-8 designating the cylinder with the misfire.
Unfortunately, the DIC code reader will not show any of the P0301-8 codes, only the more Generic P0300 even if it's only 1 cylinder having an issue.
I have an old Actron code reader that will show the P030X codes as well as the I/M monitors that the DIC shows none of. The 1st thing I would check is to see if you have a specific cylinder code still stored.
1) The generic P0300-random cylinder misfire.
2) The P030X wheer X is a number from 1-8 designating the cylinder with the misfire.
Unfortunately, the DIC code reader will not show any of the P0301-8 codes, only the more Generic P0300 even if it's only 1 cylinder having an issue.
I have an old Actron code reader that will show the P030X codes as well as the I/M monitors that the DIC shows none of. The 1st thing I would check is to see if you have a specific cylinder code still stored.
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
When the misfire stops the CEL will generally go out-depending on the problem-the code may be stored. Since you can't see P030X codes in the DIC, I would use something else to see if there is a stored P030X code.
