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Symptom Troubleshooting Index

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

When the vehicle has one of these symptoms, check for a diagnostic trouble code (DTC) with the HDS. If there is no DTC, do the diagnostic procedure for the symptom, in the sequence listed, until you find the cause.

Symptom Diagnostic procedure Also check for
Engine will not start (MIL works OK, no DTCs set)
  1. Test the battery (see BATTERY TEST ).
  2. Test the starter (see STARTER PERFORMANCE TEST ).
  3. Check the fuel pressure (see FUEL PRESSURE TEST ).
  • Low compression
  • No ignition spark
  • Intake air leaks
  • Locked up engine
  • Broken timing belt
  • Fuel contamination
Engine will not start. No communication with HDS (MIL comes on and stays on, no DTCs set) Troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
  • No power to PCM
  • No ground to PCM
MIL comes on and stays on, or never comes on at all, no DTCs set Troubleshoot the MIL circuit (see MIL CIRCUIT TROUBLESHOOTING ).  
Engine will not start (MIL works OK, no DTCs set, immobilizer indicator stays on or flashes) Check the immobilizer system (see SYSTEM CHECK ).  
Engine starts but stalls immediately (MIL works OK, no DTCs set, immobilizer indicator stays on or flashes) Check the immobilizer system (see SYSTEM CHECK ).  
Engine is hard to start (MIL works OK, no DTCs set)
  1. Test the battery (see BATTERY TEST ).
  2. Check the fuel pressure (see FUEL PRESSURE TEST ).
  3. Clean the throttle body (see THROTTLE BODY TEST ).
  • Low compression
  • Intake air leaks
  • Fuel contamination
  • Weak spark
Cold fast idle too low (MIL works OK, no DTCs set)
  1. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  2. Check the idle speed (see IDLE SPEED INSPECTION ).
  3. Clean the throttle body (see THROTTLE BODY TEST ).
  
Cold fast idle too high (MIL works OK, no DTCs set)
  1. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  2. Check the idle speed (see IDLE SPEED INSPECTION ).
 Intake air leaks
Idle speed fluctuates (MIL works OK, no DTCs set)
  1. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  2. Check the idle speed (see IDLE SPEED INSPECTION ).
  3. Do the carbon accumulation check (see THROTTLE BODY TEST ).
  4. Troubleshoot the A/C signal circuit (see A/C SIGNAL CIRCUIT TROUBLESHOOTING ).
  • Incorrect valve timing or clearance adjustment
  • Intake air leaks
After warming up, idle speed is below specification without load (MIL works OK, no DTCs set)
  1. Troubleshoot the alternator FR signal circuit (see ALTERNATOR FR SIGNAL CIRCUIT TROUBLESHOOTING ).
  2. Do the carbon accumulation check (see THROTTLE BODY TEST ).
 Incorrect valve adjustment
After warming up, idle speed is above specification without load (MIL works OK, no DTCs set)
  1. Troubleshoot the alternator FR signal circuit (see ALTERNATOR FR SIGNAL CIRCUIT TROUBLESHOOTING ).
  2. Inspect the APP sensor (see APP SENSOR SIGNAL INSPECTION ).
 Intake air leaks
After warming up, idle speed drops when steering wheel is turning (MIL works OK, no DTCs set)
  1. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  2. Troubleshoot the PSP switch signal circuit (see PSP SWITCH SIGNAL CIRCUIT TROUBLESHOOTING ).
  3. Do the carbon accumulation check (see THROTTLE BODY TEST ).
 Power steering system problem
Low power (MIL works OK, no DTCs set) Check the fuel pressure (see FUEL PRESSURE TEST ).
  • Low compression
  • Incorrect camshaft timing
  • Incorrect engine oil level
  • Exhaust restriction
Engine stalls (MIL works OK, no DTCs set)
  1. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  2. Check the fuel pressure (see FUEL PRESSURE TEST ).
  3. Check the idle speed (see IDLE SPEED INSPECTION ).
  4. Troubleshoot the brake pedal position switch signal circuit (see BRAKE PEDAL POSITION SWITCH SIGNAL CIRCUIT TROUBLESHOOTING ).
  • Intake air leaks
  • Faulty harness and sensor connections
Difficult to refuel (MIL works OK, no DTCs set)
  1. Check the fuel tank vapor control valve hose between the EVAP canister and the fuel tank.
  2. Check the fuel tank vapor recirculation tube between the fuel fill pipe and the fuel tank.
  3. Inspect the fuel filler neck for restrictions.
  4. Replace the fuel tank (see FUEL TANK REPLACEMENT ).
 Malfunctioning gas station filling nozzle
Fuel overflows during refueling (No DTCs set)
  1. Inspect the fuel filler neck for restrictions.
  2. Replace the fuel tank (see FUEL TANK REPLACEMENT ).
 Malfunctioning gas station filling nozzle
Fuel cap warning message stays on (MIL works OK, no DTCs set) Troubleshoot the fuel cap warning message system (see FUEL CAP WARNING MESSAGE SYSTEM TROUBLESHOOTING ).  
HDS does not communicate with the PCM or the vehicle Troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
  • Correct HDS software
  • Shorted reference voltage
Engine will not crank
  1. Test the battery (see BATTERY TEST ).
  2. Check the starting system (see STARTER SYSTEM CIRCUIT TROUBLESHOOTING ).
 Shorted reference voltage
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