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2008 - MX-5 - Engine

DTC P0505 [LF]



DTC P0505

Idle speed control system problem

DETECTION CONDITION

  • The PCM cannot control idle speed toward target idle speed while KOER self test.

POSSIBLE CAUSE

  • Drive-by-wire control system malfunction

  • Air cleaner element clogged

  • Air intake passage clogged

  • A/C relay control circuit malfunction

  • Generator control circuit malfunction

  • Low engine compression (Over capacity of blow-by gas)

  • PCM malfunction


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • Verify related Service Bulletins and/or on-line repair information availability.

  • Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

  • If the vehicle is not repaired, go to the next step.

No

Go to the next step.

2

VERIFY RELATED PENDING OR STORED DTC
  • Turn the ignition switch off then to the ON position. (Engine off)

  • Verify pending code or stored DTCs using the M-MDS.

  • Does DTC P0506, P0507, P0638, P2101, P2107, P2108, P2109, P2112 or P2119 presents?

Yes

Perform the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Go to the next step.

3

INSPECT ELECTRONIC THROTTLE CONTROL SYSTEM OPERATION

Yes

Go to the next step.

No

Repair or replace malfunctioning part, according to inspection results.

Then go to Step 9.

4

INSPECT A/C MAGNETIC CLUTCH OPERATION

NOTE:

  • The following test should be performed for the A/C. Go to the next step for vehicles without A/C

  • Turn the fan switch off.

  • Is the magnetic clutch still on?

Yes

Go to “A/C ALWAYS ON / A/C COMPRESSOR RUNS CONTINUOUSLY.” of ENGINE SYMPTOM TROUBLESHOOTING then go to Step 9.

(See SYMPTOM DIAGNOSTIC INDEX [LF].)

No

Go to the next step.

5

INSPECT GENERATOR CONTROL CIRCUIT MALFUNCTION
  • Apply electrical load.

  • Is the engine speed increased?

Yes

Go to the next step.

No

Repair short to power supply in generator control circuit, then go to Step 9.

6

INSPECT AIR CLEANER ELEMENT
  • Remove air cleaner element with the engine running.

  • Is the engine speed increased?

Yes

Clean or replace the air cleaner element, then go to Step 9.

(See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

7

INSPECT THROTTLE BODY PASSAGE
  • Is the throttle body clogged?

Yes

Clean or replace the throttle body passage, then go to Step 9.

No

Go to the next step.

8

INSPECT ENGINE COMPRESSION

Yes

Go to the next step.

No

Overhaul the engine, then go to the next step.

9

VERIFY TROUBLESHOOTING OF DTC P0505 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Clear the DTC using the M-MDS.

  • Perform the KOER self-test.

    (See KOEO/KOER SELF TEST [LF].)

  • Is the same DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

10

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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