P0506 - Idle Air Control (IAC) System RPM Lower Than Expected
What does that mean?
This P0506 code is one that's sometimes triggered on vehicles that have electronic throttle control. That is, they don't have a regular throttle cable from the accelerator pedal to the engine. They rely on sensors and electronics to control the throttle. In this case, the P0506 DTC (diagnostic trouble code) is triggered when the PCM (powertrain control module) detects an engine idle speed that is lower than the desired (pre-programmed) RPM.
Potential Symptoms
Most likely the only thing you'll notice is the idle speed is lower than normal so it will likely be rougher. There are potentially other symptoms as well. Of course, when trouble codes are set, the MIL (malfunction indicator lamp, a.k.a. the check engine light) illuminates.
Causes
A P0506 DTC trouble code may be caused by one or more of the following:
* A vacuum leak
* An air restriction in the intake air path or exhuast
* A faulty positive crankcase ventilation (PCV) valve
* Damaged/failed/dirty throttle body
* Internal engine problem
* Failed PCM
Possible Solutions
This DTC is more of an informational code, so if there are any other codes set, diagnose them first. If there are no other codes, inspect for vacuum leaks, restrictions, and damage. If there are no symptoms other than the DTC itself, just clear the code and see whether it returns.
P1400 - Cold Start Emission Reduction Control System
2007 GMC Truck Envoy - 2WD | Envoy, Rainier, TrailBlazer, Ascender (VIN S/T) Service Manual | Document ID: 1655997
DTC P1400 - 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.
Circuit/System Description
The catalytic converter must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalytic converter. During a cold start, the engine idle speed is elevated and spark timing is retarded to allow the catalyst to warm quickly. This diagnostic monitors the following to build an exhaust energy model:
• Engine speed
• Spark advance
• Throttle position
• Engine airflow
• Engine coolant temperature
• Engine runtime
• Park/neutral position
• Vehicle speed
The actual model is then compared to the expected exhaust energy model.
Conditions for Running the DTC
• A cold start has been detected.
• The vehicle speed is less than 2 km/h.
• The engine is at idle with no input from the accelerator pedal.
• The airflow per cylinder is greater than 80 mg/cylinder.
• DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0220, P0222, P0223, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0335, P0336, P0351, P0352, P0353, P0354, P0355, P0356, P0502, P0506, P0507, P0601, P0602, P0603, P0604, P0606, P0607, P062F, P0641, P0651, P1101, P1516, P1682, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176, P2610 are not set.
• This DTC runs for 15 seconds within the first 70 seconds of start up. This diagnostic runs once per trip when a cold start has been determined.
Conditions for Setting the DTC
The actual exhaust energy model does not match the expected exhaust energy model.
Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• 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.
Diagnostic Aids
Any loading of the engine that lowers engine RPM, such as with partial application of the clutch, during the first 70 seconds of engine run time may set this DTC.
Circuit/System Verification
Allow the engine to cool. Monitor the Cold Startup parameter. This should indicate Yes. Start and idle the engine for at least 2 minutes. DTC P1400 should run and pass.
Circuit/System Testing
• Inspect the air intake system for the following:
- If any other DTCs are set, diagnose them first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Modified, damaged, or restricted
- Dirty or deteriorating air filter element
- Crankcase ventilation system for correct operation--Refer to Crankcase Ventilation System Inspection/Description .
- Water intrusion
- Vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor
- Intake manifold leak
• Inspect the exhaust system for the following:
- Water intrusion
- Exhaust leak
- Damaged, restricted, modified or enhanced exhaust system--Refer to Symptoms - Engine Exhaust .
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Clean the Throttle Body.
Lynn Auto Repair
Jackson,TN
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