8/31/22, 9:15 PM Service Manual2006 Nubira-Lacetti Main Relay Circuit Check (1.4L/1.
6L DOHC)
Idle Air Control System Check (1.4L/1.6L DOHC)
Circuit Description
The aim of the MTIA (Main Throttle Idle Actuator) is to control the idle speed with the throttle body
itself. The throttle is motorized for low opening angle (0°C, 19°C). The characteristics of the airflow are
not the same for low and high opening angles. As a matter of fact, the gradient of the mass air flow
function of TPS is lower for small angles that permits to be more precise during the idle speed control.
Out of idle speed the throttle is actuated mechanically by a classical bowdencable.
The main throttle idle actuator (MTIA) provides a voltage signal that changes in relation to the throttle
plate angle. The signal voltage will vary from about nearly 5.0 V at idles to about 0.2V to 0.4 V at wide-
open throttle. The TPS is one of the most important inputs used by the ECM for fuel control and other
functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.
Diagnostic Aids
If the idle is too high, stop the engine. Fully extend the main throttle idle actuator (MTIA) with a IAC
driver. Start the engine. If the idle speed is above 800 rpm, locate and repair the vacuum leak. Also,
check for a binding throttle plate or throttle linkage or an incorrect base idle setting.
Idle Air Control System Check (1.4L/1.6L DOHC)
Step Action Value(s) Yes No
Perform an On-Board Diagnostic (EOBD) Go to "On-
System Check. Board
1 Is the system check complete? - Diagnostic
System
Go to Step 2 Check"
Turn the ignition switch to ON.
2 Is the Malfunction Indicator Lamp (MIL) on -
steady? Go to Step 4 Go to Step 3
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8/31/22, 9:15 PM Service Manual2006 Nubira-Lacetti Main Relay Circuit Check (1.4L/1.6L DOHC)
Step Action Value(s) Yes No
Turn the ignition switch to LOCK.
Connect the scan tool to the DLC.
3 Turn the Turn the ignition switch to ON. - Try with
Are any diagnostic trouble codes (DTCs) another scan
displayed? Go to Step 4 tool
Refer to the applicable DTC table. Go to
Is only one DTC identified as valid trouble code applicable
4 P0122? - DTC table and
go to "Multiple
Go to Step 5 DTC"
1. Connect the scan tool to the DLC.
2. Turn the ignition switch to ON.
3. Press the accelerator pedal while watching
5 TPS for smooth changes in the voltage. 0.3V-4.8V
Go
Does the scan tool show the TPS voltage change to "Diagnostic
smoothly within the value specified? Aids" Go to Step 6
1. Turn the ignition switch to lock.
2. Disconnect the MTIA connector.
3. Measure the voltage between terminal 2
6 and 8. 4.8V-5.0V
Does the voltage measure within the value
specified? Go to Step 7 Go to Step 8
Connect a fused jumper between the MTIA
connector terminal 2 and terminal 7.
7 4.8V-5.0V
Does the scan tool show the TPS voltage above
value specified? Go to Step 13 Go to Step 11
Measure the voltage between the MTIA
connector 2 and ground.
8 >5.0V
Does the voltage measure within the value
specified? Go to Step 9 Go to Step 10
1. Turn the ignition switch to lock.
2. Check for an open or low voltage in the
wire between the MTIA connector 8 and
9 -
ECM connector 19.
Is the problem found? Go to Step 12 Go to Step 14
1. Turn the ignition switch to LOCK.
2. Check for an open or low voltage in the
wire between the MTIA connector 2 and
10 -
ECM connector 79.
Is the problem found? Go to Step 12 Go to Step 14
1. Turn the ignition switch to LOCK.
2. Check for an open or low voltage in the
11 wire between the MTIA connector 7 and -
ECM connector 74.
Is the problem found? Go to Step 12 Go to Step 14
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8/31/22, 9:15 PM Service Manual2006 Nubira-Lacetti Main Relay Circuit Check (1.4L/1.6L DOHC)
Step Action Value(s) Yes No
1. Repair the wire or the connector terminal
as needed.
2. Clear any DTCs from ECM.
12 -
3. Perform the Diagnostic System Check.
Is the repair complete? System OK -
1. Replace the throttle body assembly.
2. Clear any DTCs from ECM.
13 3. Perform the Diagnostic System Check. -
Is the repair complete? System OK -
1. Turn the ignition switch to LOCK.
2. Replace the ECM.
14 3. Perform the Diagnostic System Check. -
Is the repair complete? Go to Step 15 -
Check if any additional DTCs are set. Go to
15 Are any DTCs displaced that have not been - applicable
diagnosed? DTC table System OK
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