Daewoo Matiz (2003 year). Manual - part 84

1F – 246 ENGINE CONTROLS

MAA1F070

DIAGNOSTIC TROUBLE CODE (DTC) 0505

IDLE AIR CONTROL VALVE (IACV) CIRCUIT FAULT

Circuit Description

The Engine Control Module (ECM) controls the air en-
tering into the engine with an Idle Air Control (IAC)
Valve. To increase the idle rpm, the ECM commands the
pintle inside the IAC valve away from the throttle body
seat. This allows more air to bypass through the throttle
blade. To decrease the rpm the ECM commands the
pintle towards the throttle body seat. This reduces the
amount of air bypassing the throttle blade. A scan tool
will read the IAC valve pintle position in counts. The
higher the counts, the more air that is allowed to bypass
the throttle blade. This Diagnostic Trouble Code (DTC)
determines if a low idle condition exists as defined as
100 rpm below the desired idle rpm.

Conditions for Setting the DTC

No intrusive tests are active.

DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P1133, P1134, P0171, P1171, P0172, P0201,
P0202, P0203, P0204, P0300, P0336, P0337,
P0341, P0342, P0351, P0352, P0402, P0404,
P1404, P0405, P0406, P0443, and P0502 are not
set.

Engine is running more than 60 seconds.

Barometric Pressure (BARO) is greater than 72 kPa
(10.4 psi).

Engine Coolant Temperature (ECT) is greater than
60

C (140

F).

Ignition voltage is between 11 and 16 volts.

The Intake Air Temperature (IAT) is greater than
–20

C (–4

F).

Manifold Absolute Pressure is less than 60 kPa (8.7
psi).

IAC valve is controlled fully opened.

All of the above must be met for greater than 5 sec-
onds.

Action Taken When the DTC Sets

The Malfunction Indicator Lamp (MIL) will illuminate.

The ECM will record operating conditions at the time
the diagnostic fails. This information will be stored in
the Freeze Frame and Failure Records buffers.

A history DTC is stored.

Conditions for Clearing the MIL/DTC

The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.

A history DTC will clear after 40 consecutive warm-up
cycles without a fault.

DTC(s) can be cleared by using the scan tool.

Disconnecting the ECM battery feed for more than 10
seconds.

Diagnostic Aids

Inspect the IAC valve electrical connection for proper
mating.

Inspect the wiring harness for damage.

Inspect the throttle stop screw for signs of tampering.

Inspect the throttle linkage for signs of binding or exces-
sive wear.

A slow or unstable idle may be caused by one of the fol-
lowing conditions:

Fuel system too rich or too lean.

Foreign material in the throttle body bore or in the air
induction system.

A leaking or restricted intake manifold.

ENGINE CONTROLS 1F – 247

Excessive engine overloading. Check for seized pul-
leys, pumps, or motors on the accessory drive,

Overweight engine oil.

DTC P0505 Idle Air Control Valve (IACV) Circuit Fault

Step

Action

Value(s)

Yes

Perform an On-Board Diagnostic (EOBD) System
Check.
Was the check performed?

–

Go to Step 2

Go to

“On-Board
Diagnostic

System Check”

1. Install a scan tool to the Data Link Connector

(DLC).

2. Operate the engine to idle speed.
3. Transmission in park or neutral and the parking

brake set.

4. A/C is off.
5. Using scan tool, command the Idle Air Control

(IAC) valve up and down between the specified
value.

Does the rpm change smoothly when he
commanded by the scan tool?

900–1200

rpm

Go to Step 3

Go to Step 5

1. Turn the ignition OFF.
2. Disconnect the IAC valve connector.
3. Measure the resistance between terminal C and

D of the IAC valve.

4. Measure the resistance between terminal B and A

of the IAC valve.

Is the resistance within the specified value?

40–80

Ω

Go to Step 4

Go to Step 13

1. Measure the resistance between terminal D and

B of the IAC valve.

2. Measure the resistance between terminal C and

A of the IAC valve.

Is the resistance equal to the specified value?

∞

Go to Step 15

Go to Step 13

1. Turn the ignition OFF.
2. Disconnect the IAC valve connector.
3. Turn the ignition ON.
4. With test light connected to ground, probe the

IAC connector terminals.

Does the test light illuminate on D terminals?

–

Go to Step 6

Go to Step 7

With test light connected to B+, probe the IAC
connector terminals.
Does the test light illuminate on D terminals?

–

Go to Step 8

Go to Step 9

Check for an open or short to ground in the IAC high
and low circuits and repair as needed.
Is the repair complete?

–

Go to Step 15

Go to Step 10

1. Idle the engine.
2. Connect a test light to ground, probe the IAC

connector terminals.

Does the test light flash On and OFF for all
terminals?

–

Go to Step 11

Go to Step 12

Check for an open or a short to voltage in the IAC
valve high and low circuits and repair as needed.
Is the repair complete?

–

Go to Step 15

Go to Step 10

Check the Engine control Module (ECM) connector
for poor connections and repair as needed.
Is the repair complete?

–

Go to Step 15

Go to Step 14

1F – 248 ENGINE CONTROLS

DTC P0505 Idle Air Control Valve (IACV) Circuit Fault (Cont’d)

Step

Action

Value(s)

Yes

Inspect the IAC valve passages and repair as
needed.
Is the repair complete?

–

Go to Step 15

Go to Step 13

Check the test light.
Does the test light remain on constantly for the
terminals that did not blink?

–

Go to Step 9

Go to Step 7

1. Turn the ignition OFF.
2. Replace the IAC valve.
Is the repair complete?

–

Go to Step 15

–

1. Turn the ignition OFF.
2. Replace the ECM.
Is the repair complete?

–

Go to Step 15

–

1. Using the scan tool, clear the Diagnostic Trouble

Codes (DTCs).

2. Start the engine and idle at normal operating

temperature.

3. Operate the vehicle within the Conditions for

setting this DTC as specified in the supporting
text.

Does the scan tool indicate that this diagnostic has
run and passed?

–

Go to Step 16

Go to Step 2

Check if any additional DTCs are set.
Are any DTCs displayed that have not been
diagnosed?

–

Go to

Applicable DTC

Table

System OK

ENGINE CONTROLS 1F – 249

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