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Home >> Buick >> 2004 >> Century Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 153 (Engine Controls (Troubleshooting & Diagnosis) - 3.8L) >> Troubleshooting >> Manifold Absolute Pressure (MAP) Sensor Diagnosis (With Supercharger) >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 3:  This step tests the ability of the MAP sensor to correctly indicate barometric pressure (BARO).
  1. 10:  The measurement noted in this step will be used in subsequent steps if the measurement does not exceed the specified value.
  1. 13:  This step calculates the resistance in the 5-volt reference circuit.
  1. 14:  This step calculates the resistance in the low reference circuit.
Manifold Absolute Pressure (MAP) Sensor Diagnosis (With Supercharger)

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Controls Connector End Views  or  Powertrain Control Module (PCM) 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 Inspect for the following conditions:
  • Disconnected, damaged, or incorrectly routed vacuum hoses
  • Restrictions in the manifold absolute pressure (MAP) sensor vacuum source
  • Intake manifold vacuum leaks

Did you find and correct the condition?		 - Go to Step 26  Go to Step 3 
3 
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the MAP sensor pressure with a scan tool.
  3. Observe the barometric pressure (BARO) sensor pressure with a scan tool.
  4. Compare the values.
Is the difference between the values less than the specified value?		 3 kPa Go to Step 4  Go to Step 8 
4
  1. Observe the MAP sensor pressure with a scan tool.
  2. Start the engine.
Does the MAP sensor pressure change?		 - Go to Step 5  Go to Step 8 
5
  1. Turn OFF the ignition.
  2. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
  3. Connect a J 23738-A  Mityvac to the MAP sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the MAP sensor pressure with the scan tool.
  6. Apply vacuum to the MAP sensor with the J 23738-A  in 1 in Hg increments until 15 in Hg is reached. Each 1 in Hg should decrease MAP sensor pressure by 3-4 kPa.
Is the decrease in MAP sensor pressure consistent?		 - Go to Step 6  Go to Step 8 
6 Apply vacuum with the J 23738-A  until 20 in Hg is reached.
Is the MAP sensor pressure less than the specified value?		 34 kPa Go to Step 7  Go to Step 8 
7 Disconnect the J 23738-A  from the MAP sensor.
Does the MAP sensor pressure return to the value observed in step 4 or 5?		 - System OK Go to Step 24 
8 Test for an intermittent and for a poor connection at the MAP 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 26  Go to Step 9 
9
  1. Disconnect the MAP sensor electrical connector.
  2. Observe the MAP sensor parameter with the scan tool.
Is the voltage less than the specified value?		 0.1 V Go to Step 10  Go to Step 16 
10  Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Note the measurement as "Supply voltage".
Is the voltage more than the specified value?		 5.2 V Go to Step 17  Go to Step 11 
11 Is the voltage more than the specified value? 4.8 V Go to Step 12  Go to Step 18 
12
  1. Connect a test lamp and a DMM in series between the 5-volt reference circuit and the low reference circuit of the MAP sensor, at the harness connector.
  2. Measure the amperage, with the DMM. Note the measurement as "Current flow".
Is the amperage less than the specified value?		 1 mA Go to Step 21  Go to Step 13 
13 
  1. Remove the DMM from the circuit.
  2. Connect the test lamp between the 5-volt reference circuit and the low reference circuit of the MAP sensor, at the harness connector.
  3. Measure the voltage from the 5-volt reference circuit at the test lamp to a good ground, with the DMM. Note the measurement as "Load voltage drop".
  4. Subtract the "Load voltage drop" from the "Supply voltage". Note the result as "Supply voltage drop".
  5. Divide the "Supply voltage drop" by the "Current flow".
Is the result more than the specified value?		 5 Ω Go to Step 19  Go to Step 14 
14 
  1. Measure the voltage from the low reference circuit of the MAP sensor at the test lamp to a good ground with the DMM. Note the results as "Low reference voltage drop".
  2. Divide the "Low reference voltage drop" by the "Current flow".
Is the result more than the specified value?		 5 Ω Go to Step 22  Go to Step 15 
15
  1. Remove the test lamp.
  2. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the signal circuit of the MAP sensor, at the harness connector.
  3. Observe the MAP sensor parameter with the scan tool.
Is the voltage more than the specified value?		 4.9 V Go to Step 24  Go to Step 20 
16 Test the MAP sensor signal circuit between the powertrain control module (PCM) and the MAP 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 26  Go to Step 23 
17 Test the 5-volt reference circuit between the PCM and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
18 Test the 5-volt reference circuit between the PCM and the MAP sensor for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
19 Test the 5-volt reference circuit between the PCM and the MAP sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
20 Test the MAP sensor signal circuit between the PCM and the MAP sensor for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
21 Test the low reference circuit between the PCM and the MAP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
22 Test the low reference circuit between the PCM and the MAP sensor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 26  Go to Step 23 
23 Test for shorted terminals and for poor connections at the PCM. 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 26  Go to Step 25 
24 Replace the MAP sensor. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement (L26) or Manifold Absolute Pressure (MAP) Sensor Replacement (L32) .
Did you complete the replacement?		 - Go to Step 26  -
25 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 26  -
26
  1. Reassemble the vehicle as necessary.
  2. Clear the DTCs with the scan tool.
  3. Start the engine.
  4. Operate the system in order to verify the repair.
Did you correct the condition?		 - Go to Step 27  Go to Step 2 
27 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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