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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 P2227 >> Test Description

Test Description

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

  1. 2:  This step determines if a condition exists.
  2. 7:  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. 8:  This step is testing the signal circuit. The signal circuit is pulled up to a voltage. The scan tool should display 0.00 volts when the signal circuit is grounded to the ECM housing with a fused jumper wire. If the voltage displayed on the scan tool is more than the specified value, test the signal circuit of the BARO sensor for an open or a high resistance.
  4. 9:  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.
  5. 10:  This step tests for a high resistance in the low reference circuit of the BARO sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to completely power down.
DTC P2227

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 3  Go to Step 4 
3 Is DTC P2228 or P2229 also set? - Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Step 7 
4
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the BARO sensor parameter on a scan tool while moving the related harness connectors at the barometric pressure (BARO) sensor and at the engine control module (ECM).
Does the BARO parameter remain steady and not change by more than the specified value while a related connector is being moved?		 3 kPa Go to Step 5  Go to Step 17 
5 Observe the BARO sensor parameter on a scan tool while moving the related wiring harnesses.
Does the BARO parameter remain steady and not change by more than the specified value while a related wiring harness is being moved?		 3 kPa Go to Step 6  Go to Step 18 
6
  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 7  Go to Diagnostic Aids
7 
IMPORTANT: The signal circuit of the 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 8  Go to Step 12 
8 
  1. Connect a fused jumper wire between the signal circuit of the BARO sensor and the ECM housing.
  2. Observe the BARO Volts parameter with a scan tool.
Is the voltage at the specified value?		 0 V Go to Step 9  Go to Step 13 
9 
  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 ECM housing with a DMM.
Is the amperage more than the specified value?		 80 mA Go to Step 10  Go to Step 11 
10 
  1. Turn OFF the ignition.
  2. Remove the ECM/TCM fuse from the underhood electrical center.
    3. NOTE: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
  3. Measure the resistance between the low reference circuit of the BARO sensor and the ECM housing with a DMM.
Is the resistance more than the specified valve?		 5 ohm Go to Step 14  Go to Step 15 
11
  1. Turn OFF the ignition.
  2. Test the 5-volt reference circuit of the BARO sensor for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 16 
12
  1. Turn OFF the ignition.
  2. 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 21  Go to Step 16 
13
  1. Turn OFF the ignition.
  2. Test the signal circuit of the BARO sensor for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 16 
14 Test the low reference circuit of the BARO sensor for an open or a high resistance. Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 21  Go to Step 16 
15 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 21  Go to Step 19 
16 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 21  Go to Step 20 
17 Repair the damaged connectors and terminals. Refer to Connector Repairs .
Did you complete the repair?		 - Go to Step 21  -
18 Repair the affected circuit as necessary. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 21  -
19 Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 21  -
20 Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 21  -
21
  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 22 
22 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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