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Home >> Suzuki >> 2004 >> Swift + >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 1.6L (L91) (DTC P0300 To DTC P0488) >> Diagnostic Information & Procedures >> DTC P0401 >> Test Description
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Test Description

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

  1. 3:  MAP sensor faults must be diagnosed first. A skewed MAP sensor reading could cause this DTC to set.
  2. 7:  An engine mechanical condition may cause the engine to operate poorly, which could cause a low vacuum condition.
DTC P0401

Step Action Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) 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. 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 3  Go to Intermittent Conditions
3  Is DTC P0106, P0107, or P0108 also set? Go to Diagnostic Trouble Code (DTC) List Go to Step 4 
4 Inspect the exhaust gas recirculation (EGR) system for the following conditions:
  • A vacuum leak between the EGR valve and the intake manifold
  • Signs of external leakage usually indicated by carbon buildup around the mating surfaces of the components or an audible exhaust noise
  • Restrictions in the passages or EGR valve caused by carbon deposits or casting flash

Refer to Exhaust Gas Recirculation (EGR) Valve Replacement and EXHAUST GAS RECIRCULATION (EGR) VALVE PIPE REPLACEMENT .
Did you find and correct the condition?		 Go to Step 9  Go to Step 5 
5 Inspect for leaks or restrictions at the manifold absolute pressure (MAP) sensor.
Did you find and correct the condition?		 Go to Step 9  Go to Step 6 
6 Inspect the exhaust system for the following conditions:
  • Leaks caused by damage to the exhaust components
  • Restrictions that can cause excessive back pressure and low engine vacuum - Restrictions may be caused by aftermarket equipment or damage to the exhaust components.
  • Modification of original equipment manufacture (OEM) parts

Did you find and correct the condition?		 Go to Step 9  Go to Step 7 
7 
  1. Inspect for the following engine mechanical conditions:
    • The correct installation of the timing belt
    • Worn piston rings
    • Worn camshaft
    • Other worn or damaged engine components
  2. Refer to Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91).
Did you find and correct the condition?		 Go to Step 9  Go to Step 8 
8 Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .
Did you complete the replacement?		 Go to Step 9  -
9
  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 10 
10 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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