Code P0098: Intake Air Temperature Sensor 2 Circuit High

Meaning of Error Code P0098

The generic code P0098 is a Diagnostic Trouble Code (DTC) related to the powertrain, applicable to most OBD-II equipped vehicles. It indicates that the Powertrain Control Module (PCM) has detected an abnormally high voltage (above 5 volts) in the Intake Air Temperature (IAT) sensor #2 circuit.

The PCM sends a 5-volt reference voltage to the IAT sensor, a thermistor whose resistance varies with temperature. A low resistance (due to high temperature) generates a low signal voltage, and vice versa. Code P0098 is triggered when the PCM receives a signal voltage that is too high, indicating excessive resistance in the circuit.

Symptoms of Code P0098

This code is often asymptomatic, but you may observe:

• The Malfunction Indicator Lamp (MIL) illuminated on the dashboard.
• A slight drop in performance or an increase in fuel consumption.
• In rare cases, the vehicle may enter a reduced power mode (“limp mode”).

Possible Causes of Code P0098

Several failures can cause this code:

• Faulty IAT Sensor #2: Internal failure of the thermistor.
• Connection Issues: Oxidized, loose, or corroded sensor connector.
• Wiring Problems: Short to voltage in the signal circuit or an open ground circuit.
• Electrical Interference: Wiring routed too close to high-voltage components (alternator, spark plugs).
• Faulty PCM: A rare, but possible cause.

Diagnosis and Solutions for Repairing Code P0098

Here is a step-by-step diagnostic procedure:

1. Diagnostic Tool Check: Connect an OBD2 scanner. Observe the live data for the IAT sensor #2. A constantly low reading (e.g., -40°C) or erratic reading indicates a problem.
2. Sensor and Wiring Test:
   • Disconnect the IAT sensor connector.
   • Using a jumper wire, short the signal pin to the ground pin on the harness connector.
   • The reading on the scanner should immediately reach its maximum value (e.g., > 140°C). If it does, the wiring is healthy and the sensor is most likely faulty. If not, the problem lies with the wiring or the PCM.
3. Electrical Test: Use a digital multimeter (DVOM) to check for the presence of the 5-volt reference voltage and the integrity of the circuits (no short circuits, ground continuity).
4. Visual Inspection: Carefully inspect the connector, wiring, and sensor for any signs of damage, corrosion, or burning.

Common Repairs: Replacing the faulty IAT sensor #2 or repairing the wiring/open circuit usually resolves the issue.

Related IAT Sensor Codes

P0095, P0096, P0097, P0099, P0110, P0111, P0112, P0113, P0114

Need Help?

Does electrical diagnosis seem complex? Entrust the diagnosis and repair of your vehicle to a professional mechanic equipped with the right tools for a quick and reliable solution.

What is the P0099 Code?

The P0099 error code is a generic OBD-II code related to the powertrain. It indicates that the Powertrain Control Module (PCM) has detected an intermittent or erratic signal from the Intake Air Temperature (IAT) sensor circuit #2. This issue can affect various brands (Ford, Mazda, Mercedes-Benz, etc.), although specific diagnostic procedures may vary.

Role of the IAT Sensor and Symptoms

The IAT (Intake Air Temperature) sensor is crucial for the proper functioning of the engine. The PCM uses its data, together with that from the Mass Air Flow (MAF) sensor, to calculate the optimal air-fuel ratio (typically 14.7:1) and ignition timing. A faulty signal disrupts these calculations, leading to:

• Decreased engine performance
• Increased fuel consumption
• Jerking or hesitation during acceleration
• Irregular idle
• Possible illumination of the Malfunction Indicator Lamp (MIL)

Due to its impact on the air-fuel mixture, a P0099 code should be considered serious and diagnosed promptly.

How the IAT Sensor Works

The IAT sensor is a thermistor whose electrical resistance varies with the temperature of the intake air. It is often located in the intake duct, the air filter housing, or integrated into the MAF sensor. The PCM sends it a reference voltage (usually 5V) and measures the returned voltage, which it then converts into temperature. An intermittent signal is interpreted as a fault, triggering the P0099 code.

Possible Causes of the P0099 Code

• Electrical Problems: Frayed wires, loose, oxidized, or corroded connector on the IAT sensor #2.
• Faulty Sensor: The IAT sensor #2 itself is malfunctioning.
• Air Intake Problems: A clogged air filter or a cracked air duct can distort readings.
• Problem with the MAF Sensor: A faulty MAF sensor can sometimes be related.
• Faulty PCM: More rarely, the Powertrain Control Module may be the cause.

How to Diagnose and Repair a P0099 Code?

⚠️ Safety Tip: Before starting, check your manufacturer’s Technical Service Bulletins (TSBs) to see if this issue is subject to a recall or specific procedure.

1. Visual Inspection

• Check that the IAT sensor #2 connector is properly plugged in. This is a very common cause after work on the air filter.
• Inspect the wiring and connector for signs of corrosion, damage, or loose wires.
• Check the condition of the air filter and intake duct for possible cracks or obstructions.

2. Testing with an OBD2 Scanner and Multimeter

• Using an OBD2 scanner, read the live data from the IAT sensor. The value should be plausible and change slowly when the engine is cold and then warms up.
• Use a multimeter to measure the sensor’s resistance (out of circuit) and compare it to the reference values provided by the manufacturer at different temperatures.
• Check for the presence of the reference voltage (5V) and ground at the sensor connector.

3. Corrective Actions

• Clean or tighten the electrical connector if necessary.
• Repair or replace any damaged wiring.
• If the sensor is out of specifications, replace the IAT sensor #2.
• Replace the air filter if it is dirty and repair any damaged air duct.

💡 Pro Tip

If all the wiring and the sensor are in perfect condition, the problem may come from a faulty PCM, but this is extremely rare. Check the simple causes first.

Related Codes

Codes related to temperature and air sensors: P0095, P0096, P0097, P0098, P0110, P0111, P0112, P0113.

Conclusion

The P0099 code indicates an intermittent problem with the intake air temperature sensor circuit #2. Although often simple to resolve (an unplugged connector), it should not be ignored as it affects fuel consumption and performance. A thorough visual inspection is the first step towards a successful repair.

Not comfortable with these procedures? Entrust the diagnosis to a professional mechanic for a quick and guaranteed resolution.

Diagnostic Code P009A: Definition and Meaning

Diagnostic Trouble Code P009A is a generic OBD-II code related to the powertrain. It indicates an abnormal correlation or inconsistency detected by the Powertrain Control Module (PCM) between the data from the Intake Air Temperature (IAT) sensor and the Ambient Air Temperature sensor (often located near the grille). This error code is common on many brands, including Mercedes-Benz, Jeep, Mazda, Ford, Volkswagen, and BMW.

System Operation and Sensor Roles

The PCM continuously monitors the signals from both temperature sensors. Under normal conditions (cold engine and vehicle stationary for several hours), their readings should be very similar. A significant and persistent divergence between these two values triggers the P009A code and illuminates the Malfunction Indicator Lamp (MIL).

• IAT Sensor (Intake Air Temperature): Measures the temperature of the air entering the intake manifold.
• Ambient Temperature Sensor: Measures the temperature of the air outside the vehicle.

Both sensors are Negative Temperature Coefficient (NTC) thermistors: their electrical resistance decreases as the temperature increases.

Severity and Symptoms of Code P009A

This code is considered moderate to severe. Although the vehicle may remain drivable, an untreated fault can disrupt the air-fuel mixture calculation, leading to:

• Increased fuel consumption
• Loss of power and hesitation during acceleration
• Hard cold starting
• Excessive pollutant emissions
• Sometimes, no visible symptoms other than the illuminated MIL

Possible Causes of Fault P009A

Several elements can be the source of this measurement inconsistency:

• Electrical Problems: Damaged, corroded wiring, or a disconnected/improperly seated connector on one of the sensors.
• Faulty Sensors: IAT sensor or ambient sensor out of specification or completely failed.
• Air-Related Problems: A very dirty air filter or a blocked air duct can distort the IAT sensor reading.
• PCM Failure: (Rare) An internal failure of the Powertrain Control Module that misinterprets the signals.

Step-by-Step Diagnostic Procedure

Required Tools

• OBD2 scanner to read and clear codes
• Digital Multimeter (DVOM) to measure resistance and voltage
• Technical documentation (wiring diagram) for manufacturer reference values

1. Preliminary Visual Inspection

Start with a thorough inspection. Check the condition and connection of the IAT and ambient sensors. Visually inspect the wiring for burns, cuts, or rodent damage. Ensure the air filter is clean and correctly installed.

2. Sensor Testing with a Multimeter

Disconnect the electrical connector from the suspected sensor. Using the multimeter in ohmmeter mode, measure the sensor’s resistance and compare it to the reference values provided by the manufacturer for the current ambient temperature. An infinite value (open circuit) or zero value (short circuit) indicates a faulty sensor.

3. Power and Ground Test

Reconnect the connector and turn the ignition on (without starting the engine). Using the multimeter, check for the presence of the reference voltage supply (usually 5 Volts) and a good ground at the connector pins.

4. Signal and Live Correlation Test

Use your advanced OBD2 scanner to observe the live data from both temperature sensors. Compare the displayed values. If the vehicle is cold, both temperatures should be very close. A significant discrepancy confirms the fault and indicates which sensor is providing an erroneous value.

5. Wiring Check to the PCM

If the sensors seem functional but the error persists, use the wiring diagram to check for continuity and the absence of short circuits between the sensors and the PCM.

Conclusion and Call to Action

Code P009A is often resolved by replacing a faulty sensor or repairing a loose connector. Before concluding a rare and costly PCM failure, eliminate all other possible causes. Always consult the Technical Service Bulletins (TSBs) specific to your vehicle model, as some manufacturers have released software updates to resolve this issue.

Don’t feel comfortable with these diagnostic procedures? Entrust your vehicle to a certified mechanic for professional diagnosis and reliable repair.

Code P00A0: Definition and Causes of the Fault

The fault code P00A0 is a generic powertrain code. It indicates a problem in the Charge Air Cooler Temperature Sensor circuit, specifically on engine bank 2 (the bank that does not include cylinder number 1). This code applies to many vehicles equipped with a turbocharger (Chevrolet, Ford, Toyota, Audi, VW, etc.), but diagnostic procedures may vary by model.

Role of the Sensor and the Charge Air Cooler

The turbocharger forces air into the engine to increase its power. The compressed air becomes very hot and loses density. The charge air cooler (or intercooler), whether air-to-air or air-to-liquid, functions to cool this air before it enters the engine, restore its density, and thus optimize performance and fuel economy.

The Charge Air Cooler Temperature Sensor (CACT) measures the temperature of the cooled air. The Powertrain Control Module (PCM) uses this data, often comparing it with other data (intake temperature, coolant temperature), to calculate air density and adjust the air-fuel mixture.

Note: On some models, this sensor is integrated with the Manifold Absolute Pressure (MAP) sensor.

Symptoms and Severity of Code P00A0

The severity of this code is moderate. The vehicle usually remains drivable, but it may enter a reduced power mode (“limp mode”) to protect the engine.

Common symptoms include:

• Illuminated Check Engine Light
• Noticeable decrease in engine performance
• Reduced fuel economy
• Vehicle power limitation (limp mode)
• Inhibition of diesel particulate filter regeneration (on diesel engines)

Possible Causes of the P00A0 Fault

• Faulty CACT sensor (most common cause)
• Wiring problem (short circuit, open circuit, corroded or loose connector)
• Charge air cooler clogged or damaged
• PCM failure (rare)

Diagnosis and Repair Procedures

Before starting, consult your vehicle’s Technical Service Bulletins (TSBs) for any recalls or specific procedures.

1. Visual Inspection

Inspect the sensor, its electrical connector, and the associated wiring. Look for signs of corrosion, physical damage, or loose connections. Also check the condition of the charge air cooler and air ducts for possible leaks or obstructions.

2. Sensor and Circuit Testing

Diagnostic Tool Test: Using a scan tool, observe the CACT temperature value in real time. Unplug the sensor connector. The displayed value should drop sharply. Reconnect it and check that it rises again. This confirms that the PCM is receiving the signal.

Sensor Resistance Test: With the engine off, disconnect the sensor. Measure its resistance (in Ohms) between its two terminals using a multimeter. Compare the value with the manufacturer’s specifications (it normally decreases as the temperature increases). If the value is inconsistent or infinite (open circuit), the sensor is faulty.

3. Electrical Circuit Verification

5V Power Supply: Ignition on, engine off, use a multimeter (volts) to check for the presence of a 5V reference voltage between the power supply pin of the connector and ground. No voltage? Check the continuity between this pin and the corresponding pin at the PCM to identify a possible break.

Ground: Engine off, check the continuity (ohms) between the ground pin of the connector and a good chassis ground. A lack of continuity indicates a grounding problem.

4. Conclusion and Replacement

If the sensor and wiring are in good condition and the 5V signal is present, a PCM failure is possible but rare. In most cases, replacing the faulty Charge Air Cooler Temperature Sensor will resolve the problem. After any repair, clear the fault codes with the scan tool and perform a road test to verify that the fault does not reappear.

Call to Action: This procedure is generic. For an accurate diagnosis, always refer to the specific repair manual or wiring diagrams for your vehicle model. If you are not comfortable performing these procedures, consult a professional mechanic.

What is the P00A1 Code?

The error code P00A1 is a generic powertrain code indicating a circuit problem with the Charge Air Cooler Temperature (CACT) sensor, specifically on engine bank 2. This code applies to many OBD-II equipped vehicles (Chevrolet, Ford, Toyota, Audi, VW, etc.), although precise diagnostic procedures may vary by make and model.

Role of the Sensor and the Charge Air Cooler

The turbocharger forces air into the engine to increase its power. The compressed air heats up and must be cooled by the charge air cooler (or intercooler) to increase its density before it enters the engine.

The temperature sensor (CACT) measures the air temperature at the outlet of this cooler. The PCM (Powertrain Control Module) uses this data, often comparing it with other temperatures (intake air, coolant), to optimize engine operation and turbocharger performance.

Symptoms of the P00A1 Code

• Illuminated check engine light.
• Poor performance and engine power loss.
• Reduced fuel economy.
• Activation of limp mode (“soft mode”) to protect the engine.
• Inhibition of particulate filter regeneration (on diesel vehicles).

Possible Causes of the Fault

• Faulty CACT sensor (most common cause).
• Wiring problem: open circuit, short circuit, corroded or loose connector.
• Charge air cooler clogged or damaged.
• PCM failure (rare).

Diagnostic Procedure

WARNING: This procedure is general. Always consult manufacturer-specific technical documents for an accurate diagnostic procedure.

1. Visual Inspection

Inspect the sensor, its electrical connector, and associated wiring. Look for signs of corrosion, damage, or loose connections. Also check the physical condition of the air cooler and its ducts.

2. Sensor Test (CACT)

Disconnect the sensor connector. Using a multimeter in Ohms (Ω) mode, measure the resistance between the two pins of the sensor. As the engine warms up, the resistance should gradually decrease. If the value remains infinite (open circuit) or does not change, the sensor is most likely faulty.

3. Electrical Circuit Test

Reference Voltage Test (5V): Engine off, ignition ON. Using a multimeter in DC Volts mode, check for the presence of a reference voltage of approximately 5 volts between the corresponding pin of the sensor connector (wiring side) and ground. If no voltage is present, there may be an open circuit problem or a PCM fault.

Ground Test: Check the continuity between the ground pin of the connector and a good chassis ground. A lack of continuity indicates an open circuit.

4. Consultation of Technical Bulletins

Before replacing parts, consult the manufacturer’s Technical Service Bulletins (TSB) to see if this issue is subject to a recall or specific repair procedure.

Related Codes

• P00A0: Charge Air Cooler Temperature Sensor Circuit, Bank 2
• P00A2: CACT Sensor Circuit Low Value, Bank 2
• P00A3: CACT Sensor Circuit High Value, Bank 2
• P00A4: CACT Sensor Circuit Intermittent, Bank 2

Call to Action

Diagnosing a P00A1 code can be complex. If you do not have the necessary tools or expertise, it is highly recommended to entrust the diagnosis and repair to a professional mechanic equipped with a suitable scan tool. Avoid driving for a long time with this code active to preserve your engine’s performance and integrity.