Okay, here's information regarding the OBD-II diagnostic trouble codes P0112 and P0113 on a Porsche vehicle:
**Porsche Diagnostic Trouble Code: P0112**
The **P0112** code specifically in Porsches (like your 968) indicates that the PCM has detected an Intermittent Input Signal from the Intake Air Temperature (IAT) sensor circuit. This means the signal is present sometimes, but not consistently or correctly at other times.
The **Intake Air Temperature Sensor** measures the temperature of the air entering the engine through the throttle body / Mass Air Flow (MAF) housing area. The PCM uses this information alongside MAF readings to calculate optimal fuel injection and ignition timing for various operating conditions.
**What Does It Mean?**
This code suggests a problem with the electrical signal coming from your IAT sensor *to* the PCM, characterized by inconsistency or erratic behavior. This is different than P0113 which indicates consistently low voltage/signal.
**Common Causes:**
1. **Dirty MAF Sensor:** A clogged air filter upstream can cause airflow issues that affect the IAT sensor's accuracy and potentially lead to intermittent signals.
2. **Contamination on the IAT Element:** Oil or grime buildup directly on the IAT sensor probe itself can interfere with its ability to provide consistent readings, especially at idle or under specific conditions (like temperature changes).
3. **Wiring Harness Issues (Intermittency):** Damaged wires, corroded connections, pinched harnesses, or poor grounding in the MAF/IAT area could cause intermittent signal problems unique to Porsches' complex wiring.
4. **PCM Connector Corrosion:** Water ingress into the connector housing on your Porsche's PCM can cause corrosion and contact issues with IAT sensor inputs.
**Potential Symptoms:**
* Check Engine Light illuminated
* Rough idle (engine vibrates while stationary)
* Hesitation or stumbling during acceleration
**Diagnosis and Repair:**
To resolve P0112:
* **Retrieve the Code:** Use an OBD-II scanner compatible with Porsche diagnostics.
* **Check Air Filter:** Inspect and clean/replace if necessary.
* **Clean MAF Sensor:** Sometimes cleaning the MAF sensor can indirectly help IAT issues, but focus on contamination specific to P0112 (often oil).
* **Inspect Wiring Harness:** Carefully check wiring harness condition near the sensors. This requires detailed knowledge of Porsche-specific wire routing and connectors.
* **Check PCM Connections:** Inspect for corrosion or water damage in the PCM connector area.
**Cost Estimate:**
This level of diagnostic work, especially involving MAF sensor cleaning/contamination checks or potential PCM connector issues, can be costly without specialized tools (like a VAG-COM based Porsche scan tool). It often requires labor charges from $75 to over $100 per hour for diagnosis and repair.
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**Porsche Diagnostic Trouble Code: P0113**
The **P0113** code indicates that the PCM has detected an Intermittent High Input signal from the IAT sensor circuit. This means the voltage or resistance reading is consistently high (or too low, depending on the sensor type) when it shouldn't be.
Again, we're dealing with your Porsche's **Intake Air Temperature Sensor** providing incorrect temperature data to the PCM.
**What Does It Mean?**
This code suggests a problem where the IAT signal voltage or resistance value is consistently high (or too low for P0113). A common reason for a *high* reading might be the sensor actually being in cold air instead of the heated intake stream, but other factors like wiring short circuits can also cause this.
**Common Causes:**
1. **Broken Wires:** Shorted or broken wires connected to the IAT sensor probe (e.g., ground wire).
2. **PCM Connector Issues:** Similar corrosion or damage in the PCM connector for IAT signals as seen with P0112.
3. **Vacuum Leak Before Throttle Body/MAF:** Leaks that draw cold air into the system can physically displace the heated IAT sensor probe (or affect its signal) if it's installed slightly off or not perfectly sealed in Porsche configurations.
**Potential Symptoms:**
* Check Engine Light illuminated
* Rough idle, hesitation during acceleration
**Diagnosis and Repair:**
To resolve P0113:
* **Retrieve the Code:** Use an OBD-II scanner compatible with Porsche.
* **Check Wiring:** Verify wiring for shorts or breaks specifically related to IAT signals. This can be tricky without a proper diagnostic tool.
* **Inspect PCM Connections:** Check connectors again, looking closely at grounds and power supply lines (if accessible).
* **Verify Sensor Placement/Function:** Ensure the heated air intake probe is correctly positioned in Porsche's specific MAF housing. Sometimes relocating it helps.
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Both P0112 and P0113 codes point to problems with your IAT sensor system, which can significantly affect engine performance due to incorrect fueling calculations based on faulty temperature data for airflow. Using a specialized diagnostic tool is highly recommended for accurate pinpointing of the issue.
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