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Jason
Jason, Auto Service Technician
Category: Chevy
Satisfied Customers: 288
Experience:  ASE MASTER TECH L1 ADVANCED DIAG, 18 YEARS EXP, 6 YEARS GM TECH, 12 YEARS ALL MAKES ALL MODELS
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2003 Chevrolet Impala: check engine codes 300 404..Spark plugs

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check engine codes 300 404 for a 2003 Chevrolet Impala with 80k miles. Spark plugs have been replaced. Car has a bad EBCN on it.
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P0404

Circuit Description

The exhaust gas recirculation (EGR) valve position sensor is monitored by the powertrain control module (PCM). The 5-volt reference circuit, low reference circuit and the EGR valve position signal circuit are used by the PCM to determine the EGR valve position. The PCM compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed. If the PCM detects a calibrated difference between the EGR Position Sensor parameter and desired EGR Position parameter for a calibrated amount of time, when the EGR valve is commanded open, DTC P0404 sets.

Conditions for Running the DTC

  • The Ignition 1 Signal parameter is more than 11 volts.
  • The EGR command will be disabled if the startup engine coolant temperature (ECT) is less than 5°C (41°F) and will not enable until the ECT is more than 75°C (167°F).
  • The EGR valve is commanded to open.
  • The EGR flow test is not active.

Conditions for Setting the DTC

  • The difference between the EGR Position Sensor parameter and the desired EGR Position parameter is more than 15 percent
  • The above condition is met for more than 20 seconds

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

  • Inspect for excessive deposits on the EGR pintle or seat. Inspect for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.
  • If the condition is intermittent, refer to Intermittent Conditions.

 

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SYSTEM DESCRIPTION
The powertrain control module (PCM) uses information from the ignition control (IC) module 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

  • DTCs P0101, P0102, P0103, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0336, P0341, P0502, P0503, P1106, P1107, P1114, P1115, P1121, P1122, P1336, P1351, P1352, P1361, P1362, P1374 are not set.
  • The engine speed is between 525-5,900 RPM .
  • The ignition voltage is between 9-18 volts .
  • The engine coolant temperature (ECT) is between -7 and +125°C (21-255°F) .
  • The fuel level is more than 10 percent

.

  • The throttle position (TP) sensor 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.
  • Worn or damaged accessory drive belt.
  • Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

TEST DESCRIPTION

Steps 1-3

Steps 4-6

Step 7

Steps 8-10

Steps 11-17

Steps 18-23

The number below refers to the step number on the diagnostic table.

 

  1. If the actual CKP variation values are not within the learned values, the misfire counters may increment.
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Customer: replied 6 years ago.
Car is not with me Son has it in Akron Ohio. Should I have the EGR replaced first? He is not from the area and is new in town. I am in Dallas Texas. Since this car has a bad EBCM that is waiting to be replaced would that cause the PCM to act up?

yes, replace egr, this would be the most likley cause, if no diag is possible, and no the ebcm would not cause these codes. and if the egr is bad it can cause missfires as well.