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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1071 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P2142 To P2279)) >> Diagnosis >> DTC P2227 (California RPO YF5, NE1, and VCL) >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 4:  This step tests the ability of the BARO sensor to correctly indicate barometric pressure. The value shown for the BARO sensor varies with altitude and weather conditions.
  2. 7:  This step disables the EGR system in order to determine if the EGR vacuum sensor is receiving vacuum unnecessarily.
  3. 8:  This step tests for a sensor that is stuck in range.
DTC P2227 (California RPO YF5, NE1, and VCL)

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Turn OFF the ignition.
  2. Inspect the barometric pressure (BARO) sensor for a plugged port.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 3 
3
IMPORTANT: The vehicle that is used for a comparison is not limited to the same type of vehicle that is being serviced. A vehicle known to provide an accurate BARO reading is acceptable.
Do you have access to another vehicle in which the BARO parameter can be observed with a scan tool?		 - Go to Step 4  Go to Step 5 
4 
  1. Start the engine.
  2. Allow the engine to reach operating temperature.
  3. Observe the BARO parameter with a scan tool.
  4. Start the engine of the known good vehicle.
  5. Allow the engine to reach operating temperature.
  6. Observe the BARO parameter of the known good vehicle with a scan tool.
  7. Compare the values.
Is the difference between the values less than the specified value?		 5 kPa Go to Step 6  Go to Step 10 
5
IMPORTANT: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure, and/or very low or very high temperature, may cause a reading to be slightly out of range.
  1. Start the engine.
  2. Allow the engine to reach operating temperature.
  3. Observe the BARO parameter with a scan tool. Refer to Altitude vs Barometric Pressure .
  4. The BARO parameter should be within the range specified for your altitude.
Does the BARO sensor indicate the correct barometric pressure?		 - Go to Step 6  Go to Step 10 
6
  1. Turn OFF the ignition.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the BARO parameter and the EGR Vacuum Sensor parameter with a scan tool.
  4. Compare the values.
Is the difference between the values less than the specified value?		 5 kPa Go to Step 7  Go to Step 15 
7 
  1. Start the engine.
  2. Ensure that the engine coolant temperature (ECT) is more than 60° C (140° F).
  3. Allow the engine to idle.
  4. Command the exhaust gas recirculation (EGR) system to the sealed state with a scan tool. Refer to Scan Tool Output Controls .
  5. Observe the BARO parameter and the EGR Vacuum Sensor parameter with the scan tool.
  6. Compare the values.
Is the difference between the values more than the specified value?		 5 kPa Go to Step 33  Go to Step 8 
8 
  1. Turn OFF the ignition.
  2. Connect a J 23738-A  Mityvac vacuum pump to the BARO sensor port.
  3. Turn ON the ignition, with the engine OFF.
  4. Monitor the BARO parameter with the scan tool.
  5. Apply vacuum with the J 23738-A  SLOWLY 1 inch Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the BARO sensor pressure.
  6. Increase the vacuum to 20 inches Hg.
Does the BARO parameter decrease smoothly through the test?		 - Go to Step 9  Go to Step 10 
9 Disconnect the J 23738-A  from the BARO sensor port.
Does the BARO sensor pressure return to the original value that was observed in Step 4 or 5?		 - Go to Intermittent Conditions Go to Step 35 
10
  1. Turn OFF the ignition.
  2. Disconnect the BARO sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the BARO parameter with the scan tool.
Is the pressure more than the specified value?		 14 kPa Go to Step 24  Go to Step 11 
11 Measure the voltage from the 5-volt reference circuit of the BARO sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage more than the specified value?		 5.2 V Go to Step 20  Go to Step 12 
12
  1. Connect a jumper wire between each of the terminals in the BARO sensor harness connector and the corresponding terminal at the BARO sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  2. Measure the voltage from the 5-volt reference circuit of the BARO sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage less than the specified value?		 4.80 V Go to Step 23  Go to Step 13 
13
  1. Remove the jumper wires.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the BARO sensor and the signal circuit of the BARO sensor.
  3. Observe the BARO parameter with the scan tool.
Is the pressure more than the specified value?		 200 kPa Go to Step 14  Go to Step 22 
14
  1. Remove the jumper wire.
  2. Connect a jumper wire between each of the terminals in the BARO sensor harness connector and the corresponding terminal at the BARO sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  3. Measure the voltage from the low reference circuit of the BARO sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage more than the specified value?		 0.2 V Go to Step 21  Go to Step 31 
15
  1. Disconnect the EGR vacuum sensor electrical connector.
  2. Observe the EGR Vacuum Sensor parameter with the scan tool.
Is the pressure more than the specified value?		 13 kPa Go to Step 29  Go to Step 16 
16 Measure the voltage from the 5-volt reference circuit of the EGR vacuum sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage more than the specified value?		 5.2 V Go to Step 25  Go to Step 17 
17
  1. Connect a jumper wire between each of the terminals in the EGR vacuum sensor harness connector and the corresponding terminal at the EGR vacuum sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  2. Measure the voltage from the 5-volt reference circuit of the EGR vacuum sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage less than the specified value?		 4.80 V Go to Step 28  Go to Step 18 
18
  1. Remove the jumper wires.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the EGR vacuum sensor and the signal circuit of the EGR vacuum sensor.
  3. Observe the EGR Vacuum Sensor parameter with the scan tool.
Is the pressure more than the specified value?		 200 kPa Go to Step 19  Go to Step 27 
19
  1. Remove the jumper wire.
  2. Connect a jumper wire between each of the terminals in the EGR vacuum sensor harness connector and the corresponding terminal at the EGR vacuum sensor. Refer to Using Connector Test Adapters in Wiring Systems.
  3. Measure the voltage from the low reference circuit of the EGR vacuum sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage more than the specified value?		 0.2 V Go to Step 26  Go to Step 30 
20 Test the 5-volt reference circuit of the BARO sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
21 Test the low reference circuit of the BARO sensor for high resistance or an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
22 Test the signal circuit of the BARO sensor for the following conditions:
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
23 Test the 5-volt reference circuit of the BARO sensor for an open or for a high resistance.
Refer to Testing for Continuity andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
24 Test the signal circuit of the BARO sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
25 Test the 5-volt reference circuit of the EGR vacuum sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
26 Test the low reference circuit of the EGR vacuum sensor for high resistance or an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
27 Test the signal circuit of the EGR vacuum sensor for the following conditions:
  • A short to ground
  • An open
  • A high resistance

Refer to Testing for Continuity andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
28 Test the 5-volt reference circuit of the EGR vacuum sensor for an open or for high resistance.
Refer to Testing for Continuity andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 32 
29 Test the signal circuit of the EGR vacuum sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
30 Test for an intermittent and for a poor connection at the EGR vacuum sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 34 
31 Test for an intermittent and for a poor connection at the BARO sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 35 
32 Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
33
  1. Inspect for any mis-routed vacuum lines in the EGR system that would cause unwanted vacuum to be supplied to the EGR vacuum sensor. Refer to Emission Hose Routing Diagram .
  2. Repair as necessary.
Did you complete the repair?		 - Go to Step 37  -
34 Replace the EGR vacuum sensor. Refer to Exhaust Gas Recirculation (EGR) Valve Vacuum Sensor Replacement .
Did you complete the replacement?		 - Go to Step 37  -
35 Replace the BARO sensor. Refer to Barometric Pressure (BARO) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 37  -
36 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 37  -
37
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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 38 
38 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
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