DTC P0505: Idle Control System Malfunction

NOTE: If DTC P1508 or P1509 is set, trouble shoot DTC P1508 or P1509 before trouble shooting DTC P0505.

Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral, until radiator fan comes on. Allow engine to idle. Using scan tool, ensure throttle position is approximately 10 percent with throttle fully closed. Ensure engine coolant temperature is 176-212°F (80-100°C). If throttle position or engine coolant temperature are not within specification, repair faulty sensor circuit.
On Canadian models, set parking brake and ensure headlights are off. Using scan tool, check engine speed with no loads (headlights, blower motor, rear defogger, radiator cooling fan and A/C off). See IDLE SPEED SPECIFICATION . If engine speed is not within specification, go to next step. If engine speed is within specification, problem is intermittent, system is okay at this time.
If engine speed is 620 RPM or less on D16Y7 M/T and D16Y8 or 650 or less on D16Y7 A/T and B16Y2, go to next step. If engine speed is not as specified, check engine coolant level and for air in cooling system. Check for vacuum leaks and ensure throttle valve is completely closed. Repair as necessary. Adjust base idle speed to specification. See the ADJUSTMENTS article. If idle speed will not adjust to specification, replace IAC valve.

Disconnect IAC valve 2-pin (3-pin on D16Y7 and D16Y8 A/T) connector. If idle speed decreases or engine stalls, adjust base idle speed to specification. See the ADJUSTMENTS article. If idle speed will not adjust to specification, clean throttle body ports. If idle speed does not decrease or engine does not stall, replace IAC valve.

IDLE SPEED SPECIFICATIONS

Application

RPM

B16A2 Engine

⁽¹⁾⁽²⁾⁽³⁾ 400-500

⁽¹⁾⁽²⁾⁽⁴⁾ 650-750

⁽¹⁾⁽²⁾⁽⁵⁾ 700-800

⁽¹⁾⁽²⁾⁽⁶⁾ 760-860

D16Y7 Engine

A/T

⁽¹⁾⁽²⁾⁽⁷⁾ 650-750

⁽¹⁾⁽²⁾⁽⁶⁾ 760-860

M/T

⁽¹⁾⁽²⁾⁽⁷⁾ 620-720

⁽¹⁾⁽²⁾⁽⁶⁾ 760-860

D16Y8 Engine

A/T

⁽¹⁾⁽²⁾⁽⁷⁾ 650-750

⁽¹⁾⁽²⁾⁽⁶⁾ 760-860

M/T

⁽¹⁾⁽²⁾⁽³⁾ 400-500

⁽¹⁾⁽²⁾⁽⁴⁾ 620-720

⁽¹⁾⁽²⁾⁽⁵⁾ 700-800

⁽¹⁾⁽²⁾⁽⁶⁾ 760-860

⁽¹⁾	USA models.

⁽²⁾	Canadian models.

⁽³⁾	With Idle Air Control (IAC) valve disconnected, transmission in Neutral or Park and no load (headlights, blower motor, rear defogger, A/C and cooling fan off). On Canadian models, set parking brake and ensure headlights are off.

⁽⁴⁾

Turn ignition off and reset PCM by removing BACK UP (7.5-amp) fuse, located in underhood fuse/relay box for 10 seconds. With Idle Air Control (IAC) valve connected, transmission in Neutral or Park and no load (headlights, blower motor, rear defogger, A/C and cooling fan off). On Canadian models, set parking brake and ensure headlights are off.

⁽⁵⁾	Check after one minute with headlights on low.

⁽⁶⁾	Turn headlights off and check after one minute with blower motor on HIGH and A/C on.

⁽⁷⁾	Check with Idle Air Control (IAC) valve and Intake Air Temperature (IAT) sensor connected, transmission in Neutral or Park and no load (headlights, blower motor, rear defogger, A/C and cooling fan off). On Canadian models, set parking brake. Ensure headlights are off.