GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2008 🢒 I-370 🢒 Engine 🢒 Engine Controls and Fuel - 2.9L 🢒 DTC P0506 or P0507

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0506: Idle Speed Low

DTC P0507:  Idle Speed High

Circuit/System Description

The throttle actuator control (TAC) motor is controlled by the engine control module (ECM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the ECM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the ECM commands the throttle plate open allowing more air to pass the throttle plate.

Conditions for Running the DTC
    • DTCs P0068, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0220, P0300, P0336, P0442, P0446, P0452, P0453, P0641, P0651, P1516, P2101, P2135, P2176 are not set.
    • The engine is operating for at least 60 seconds.
    • The engine coolant temperature (ECT) is more than 60°C (140°F).
    • The intake air temperature (IAT) is more than -20°C (-4°F).
    • The barometric pressure (BARO) is more than 70 kPa.
    • The system voltage is between 11-18 volts.
    • The vehicle speed is less than 2 km/h (1 mph).
    • The engine has been idling for greater than 10 seconds.
    • The AC mode state has not changed.
    • The power steering load state has WOT changed.
    • The transmission gear selector state has not changed.
    • DTC P0506 and P0507 run continuously when the above conditions are met.

Conditions for Setting the DTC

P0506

    • The actual idle speed is approximately 100 RPM lower than the desired idle speed.
    •  The above condition is present for 15 seconds.

P0507

    • The actual idle speed is approximately 200 RPM greater than the desired idle speed.
    •  The above condition is present for 15 seconds.

Action Taken When the DTC Sets

DTCs P0506 and P0507 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0506 and P0507 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. If there are any other DTCs set, diagnose those first.
  2. Using a scan tool compare the desired engine idle speed to the actual engine idle speed.
    3. • Actual engine idle speed should be no greater than 100 RPM below desired.
    • Actual engine idle speed should be no greater than 200 RPM above desired.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Inspect for any condition that can reduce idle speed by increasing engine load.
    2. • Incorrect torque converter clutch (TCC) operation
    • Accessories that require additional torque to operate
    • Excessive deposits in the throttle body
    • Restricted exhaust
    • Mechanical conditions that limit engine speed
  2. Inspect for the following conditions:
    3. • Vacuum leaks
    • A faulty positive crankcase ventilation (PCV) valve

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.