P0548 – Exhaust Gas Temperature Sensor Circuit High (Bank 2, Sensor 1)

Urgency and Severity

If your vehicle is displaying the P0548 code, it indicates a problem with the exhaust gas temperature (EGT) sensor circuit on bank 2, sensor 1. While you can usually continue driving safely in the short term, it's best to diagnose and repair this issue promptly to prevent potential catalytic converter damage from overheating. If the check engine light is flashing, you should stop driving immediately and have the vehicle towed to a repair shop, as this indicates a severe misfire that could damage the catalytic converter.

Code Specifics

The P0548 is a generic powertrain code that applies to all makes and models from 1996 onwards. However, the specific troubleshooting steps may vary slightly between vehicle manufacturers.

The code sets when the powertrain control module (PCM) detects that the voltage from the bank 2 EGT sensor 1 circuit is below the expected range for a specified amount of time, usually under 0.2 volts.

Affected Components

The main components involved when the P0548 code triggers are:

• Exhaust Gas Temperature (EGT) Sensor 1 on Bank 2
• EGT Sensor Wiring and Connectors
• Powertrain Control Module (PCM)

The EGT sensor is a thermistor located in the exhaust manifold or front exhaust pipe. It measures exhaust gas temperatures between 260-1,000°C (500-1,832°F) to allow the PCM to protect the catalytic converter from damage due to overheating. Bank 2 refers to the side of the engine that does not contain cylinder #1.

Common Causes

Potential causes that can trigger the P0548 code include:

• Faulty EGT sensor (most common)
• Damaged or corroded wiring and connectors
• Short circuit to ground in the wiring harness
• Failure in the PCM (rare)

Diagnosis Steps

To properly diagnose the P0548 code, follow these steps:

1. Scan for all codes and document them. Clear the codes and test drive to see if P0548 returns.

2. Visually inspect the wiring and connectors between the EGT sensor and PCM. Look for damaged, burnt, corroded, or loose wires.

3. With the ignition on, test the reference voltage to the EGT sensor. It should be around 5 volts. If the reading is off, suspect an issue with the PCM or wiring.

4. Conduct a resistance test on the EGT sensor. Compare the readings to manufacturer specifications, which typically range from 185 ohms at 260°C (500°F) to 30 ohms at 1,000°C (1,832°F). Replace the sensor if measurements are out of range.

5. If no problems are found, suspect a failure in the PCM, although this is rare.

Repair Solutions

Fixes for the P0548 code may involve:

• Replacing the EGT sensor
• Repairing damaged wiring or connectors
• Reflashing or replacing the PCM in rare cases

An EGT sensor replacement typically costs between $130-$200 (€110-€170), while wiring repairs are around $100-$300 (€85-€255) depending on the extent of the damage. PCM replacement is much more expensive at $800-$1,500 (€680-€1,275).

Prevention and Related Codes

Proper maintenance, including replacing faulty oxygen sensors and fixing exhaust leaks promptly, can help prevent EGT sensor issues. Codes P0546 and P0549 are closely related, but refer to the EGT sensor on bank 1 instead. Other codes that may appear alongside P0548 can indicate misfires, lean conditions, or air-fuel mixture problems.

Hopefully this in-depth look at the P0548 code helps your readers better understand this exhaust system issue. As always, proper diagnosis with quality scan tools is essential for an effective repair.

Frequently Asked Questions About P0548

What does the P0548 code mean?

The P0548 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the exhaust gas temperature (EGT) sensor circuit for bank 2, sensor 1. This means there is an issue with the wiring, connector, sensor, or PCM.

Is it safe to drive with a P0548 code?

While it’s usually safe to drive with a P0548 code in the short term, it’s best to diagnose and repair the issue promptly. Driving with a faulty EGT sensor can lead to increased emissions and potential catalytic converter damage.

What are the common symptoms of a P0548 code?

The most common symptom is an illuminated check engine light. In some cases, you may notice reduced engine performance or increased fuel consumption. However, there may be no noticeable symptoms other than the stored code.

What causes a P0548 code?

Common causes include a faulty EGT sensor, damaged wiring or connectors, a short to ground in the wiring harness, or a problem with the PCM. Less common causes include a low battery voltage or poor electrical connections.

How do you diagnose a P0548 code?

Diagnosis involves scanning for codes, visually inspecting wiring and connectors, testing reference voltage and resistance at the EGT sensor, and checking for proper PCM operation. A professional mechanic will follow the manufacturer’s diagnostic procedures.

Can a P0548 code clear itself?

While it’s possible for a P0548 code to clear itself if the condition was temporary, such as a loose connection, it’s more likely that the code will remain until the underlying issue is fixed and the code is cleared with a scan tool.

How much does it cost to fix a P0548 code?

The cost to repair a P0548 code varies depending on the cause. An EGT sensor replacement typically costs between $130-$200, while wiring repairs may range from $100-$300. PCM replacement is more expensive at $800-$1,500.

Can a bad O2 sensor cause a P0548 code?

No, a bad oxygen sensor will not directly cause a P0548 code, as this code is specific to the EGT sensor circuit. However, a faulty O2 sensor can cause other codes and driveability issues.

What does bank 2 mean in the P0548 code?

Bank 2 refers to the side of the engine that does not contain cylinder #1. In a transverse mounted 4-cylinder engine, bank 2 is typically the rear bank. In V6 or V8 engines, bank 2 is usually the passenger side bank.

How do I locate the EGT sensor for a P0548 code?

The EGT sensor is typically located in the exhaust manifold or front exhaust pipe before the catalytic converter. On turbocharged engines, it may be near the turbocharger. Consult a vehicle-specific repair manual for the exact location.

Can a P0548 code affect emissions?

Yes, a faulty EGT sensor can cause increased emissions, as it may prevent the PCM from properly adjusting the air-fuel ratio or timing to protect the catalytic converter from overheating. This can lead to a failed emissions test.

Will a P0548 code prevent my car from passing inspection?

In most areas, a stored P0548 code will cause your vehicle to fail an OBD-II emissions inspection. The code must be properly diagnosed and repaired, and the readiness monitors must be reset before retesting.

How long does it take to fix a P0548 code?

The repair time for a P0548 code depends on the specific cause. An EGT sensor replacement typically takes 1-2 hours, while wiring repairs may take 2-3 hours. PCM replacement and programming can take 3-5 hours.

Can a P0548 code be caused by an aftermarket exhaust?

Yes, if an aftermarket catless exhaust has been installed without provisions for the EGT sensor, or if the sensor is not functioning correctly due to the change in backpressure, it can cause a P0548 code to set.

What are some related codes to P0548?

Related codes include P0546 and P0549, which refer to high voltage and circuit issues for the bank 1 EGT sensor. Other related codes may include P0420 (catalyst efficiency low), P0300 (random misfire), and fuel trim codes.

Can a P0548 code cause damage to my engine?

While a P0548 code itself does not cause direct engine damage, driving with a faulty EGT sensor can lead to catalytic converter damage due to uncontrolled exhaust temperatures. This can result in costly repairs if not addressed promptly.

How often should I replace my EGT sensor?

There is no specific maintenance schedule for EGT sensors. They are typically replaced only when a problem is detected, such as a stored code or failed emissions test. With proper care, an EGT sensor can last the lifetime of the vehicle.

Can I replace the EGT sensor myself?

Replacing an EGT sensor is a moderately difficult repair that requires basic tools and mechanical skills. However, it’s important to follow the manufacturer’s procedures and torque specifications to ensure proper operation and prevent exhaust leaks.

What should I do if I get a P0548 code?

If you get a P0548 code, it’s best to have the vehicle diagnosed by a professional mechanic who can properly identify the cause and recommend the appropriate repairs. Continuing to drive with a faulty EGT sensor can lead to more costly issues.

Can a P0548 code come back after repair?

If the root cause of the P0548 code was not properly addressed, or if there are other underlying issues, the code may come back after repair. It’s important to perform thorough diagnosis and testing to ensure the problem is fully resolved.