The Electronic Throttle Control (ETC) System uses various inputs from the powertrain control module (PCM). This system uses the inputs to control the idle speed through serial data circuits to the throttle actuator control (TAC) module. The DC motor, which is located on the throttle body, activates the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed, reducing air flow into the engine, and the idle speed decreases. In order to increase the idle speed, the TAC module commands the throttle plate open, allowing more air in order to bypass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0506 sets.
This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
• | DTCs P0101-P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0125, P0171, P0172, P0174, P0175, P0200, P0220, P0300, P0440, P0442, P0443, P0496, P0500, P0502, P0503, P2135 are not set. |
• | The engine is running for more than 60 seconds. |
• | The engine coolant temperature (ECT) is more than 60°C (140°F). |
• | The intake air temperature (IAT) is more than -10°C (+14°F). |
• | The barometric pressure (BARO) is more than 65 kPa. |
• | The system voltage is between 9-18 volts. |
• | The vehicle speed is less than 1.7 km/h (1 mph). |
• | The accelerator pedal position (APP) sensor is at 0 percent. |
• | DTC P0506 runs continuously once the above conditions are met. |
The PCM detects that the actual idle speed is 100 RPM less than the desired idle speed for 5 continuous seconds.
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No | ||||||
---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Component Views or Powertrain Control Module Connector End Views | |||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||
Did the engine speed stay within 100 RPM of the commanded RPM during the above test? | Go to Step 3 | Go to Step 4 | |||||||
3 |
Does the DTC set? | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||
4 | Inspect for the following conditions:
Did you find and correct the condition? | Go to Step 5 | -- | ||||||
5 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 6 | ||||||
6 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK |
The engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by 2 circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.
This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
• | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0128, P0171, P0172, P0174, P0175, P0200, P0230, P0300, P0442, P0443, P0446, P0449, P0455, P0461, P0462, P0463, P0464, P0496, P1111, P1112, P1114, P1115, P1121, P1122, P1380, P1381 are not set. |
• | The Engine Run Time parameter is more than 60 seconds. |
• | The ECT Sensor parameter is more than 60°C (140°F). |
• | The IAT Sensor parameter is more than -10°C (+14°F). |
• | The TP Sensor parameter is less than 0.7 percent. |
• | The BARO parameter is more than 65 kPa. |
• | The Vehicle Speed Sensor parameter is less than 1.6 km/h (1 mph). |
• | The Ignition 1 Signal parameter is between 9-18 volts. |
• | There is no additional electrical load. |
• | The above conditions are met for more than 2 seconds. |
• | DTC P0506 runs continuously when the above conditions are met. |
The actual engine speed is 100 RPM less than the desired engine speed for more than 5 seconds.
• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
Inspect for the following conditions:
• | High resistance in an IAC valve control circuit |
• | Restricted air intake system |
• | Proper operation and installation of all air intake components |
• | Collapsed, clogged, or loose air intake ducts |
• | A clogged air filter |
• | Proper operation of the mass air flow (MAF) sensor, if equipped |
• | A tampered with or damaged throttle stop screw |
• | A tampered with or damaged throttle plate, throttle shaft, or throttle linkage |
• | Objects blocking the IAC passage or throttle bore |
• | Excessive deposits in the IAC passage or on the IAC pintle |
• | Excessive deposits in the throttle bore or on the throttle plate |
• | Vacuum leaks |
• | A low or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve--Refer to Symptoms - Engine Controls . |
If the problem is determined to be intermittent, refer to Testing for Intermittent Conditions and Poor Connections .
The numbers below refer to the step numbers on the diagnostic table.
This test will determine the ability of the PCM and the IAC valve control circuits to control the IAC valve.
This test will determine the ability of the PCM to provide the IAC valve control circuits with a ground. On a normal operating system, the test lamp should not flash while the IAC Counts are incrementing.
Step | Action | Yes | No | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | |||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||||
2 |
Important: Ensure that the Engine Speed parameter stabilizes with each Commanded RPM change to determine if the engine speed stays within 100 RPM of the Commanded RPM.
Did the Engine Speed parameter stabilize within 100 RPM of the commanded RPM? | Go to Step 3 | Go to Step 4 | ||||||||||||||
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids | ||||||||||||||
4 |
Did the Engine Speed parameter steadily decrease to 600 RPM and steadily increase to 1,700 RPM when the IAC valve was commanded in and out? | Go to Step 5 | Go to Step 11 | ||||||||||||||
Did the test lamp remain ON, never flashing, while the IAC Counts were incrementing for any of the IAC valve control circuits? | Go to Step 10 | Go to Step 6 | |||||||||||||||
6 | Did the test lamp remain OFF, never flashing, while the IAC Counts were incrementing for any of the IAC valve control circuits? | Go to Step 9 | Go to Step 7 | ||||||||||||||
Did the test lamp stay illuminated and never flashing while the IAC Counts were incrementing for any of the IAC valve control circuits? | Go to Step 8 | Go to Step 16 | |||||||||||||||
8 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 12 | ||||||||||||||
9 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 12 | ||||||||||||||
10 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 12 | ||||||||||||||
11 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 14 | ||||||||||||||
12 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 13 | ||||||||||||||
13 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 16 | ||||||||||||||
14 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 15 | ||||||||||||||
15 | Replace the throttle body. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | Go to Step 17 | -- | ||||||||||||||
16 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | -- | ||||||||||||||
17 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 18 | ||||||||||||||
18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK |