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Home >> Cadillac >> 2006 >> STS Base, 3.6 7, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 3.6L - DTC P2178 To U0423 >> DTC P2228 >> Test Description
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Test Description

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

  1. 2:  This step determines if a condition exists.
  2. 4:  This step is testing the signal circuit. The signal circuit is pulled up to a voltage, so the scan tool should display a voltage within the specified range. If the voltage is low, this indicates the signal circuit is grounded.
  3. 5:  The ECM produces a measurable steady-state amperage that provides the 5-volt reference to the BARO sensor. If the amperage on the 5-volt reference circuit is less than the specified value, test the 5-volt reference circuit for an open, a high resistance, or for a short to ground.
DTC P2228

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Clear the diagnostic trouble codes (DTCs) with a scan tool.
  3. Start the engine.
  4. Observe the DTC information with a scan tool.
Does the DTC fail this ignition?		 - Go to Step 4  Go to Step 3 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 4  Go to Diagnostic Aids
4 
IMPORTANT: The signal circuit of the barometric pressure (BARO) sensor is pulled up to a voltage through a 1 mega-ohm resistor.
  1. Turn OFF the ignition.
  2. Disconnect the BARO sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the BARO Volts parameter with a scan tool.
Is the voltage within the specified range?		 4.9-5.2 V Go to Step 5  Go to Step 7 
5 
  1. Set-up a DMM to test amperage on the 400 mA scale.
  2. Measure the amperage between the 5-volt reference circuit of the BARO sensor and the engine control module (ECM) housing with a DMM.
Is the amperage more than the specified value?		 80 mA Go to Step 8  Go to Step 6 
6
  1. Turn OFF the ignition.
    2. IMPORTANT: The ECM for this engine is not equipped with 5-volt reference DTCs. The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.
  2. Test the 5-volt reference circuit of the BARO sensor and all shared 5-volt reference circuits for an open, short to ground, or for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
7 Test the signal circuit of the BARO sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
8 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 .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 10 
9 Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
10 Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11 Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 12  -
12
  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 13 
13 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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