P0428 Code – Catalyst Temperature Sensor High (Bank 1) Explained

🔍 What Does Code P0428 Mean?

P0428 indicates that the catalyst temperature sensor (Bank 1) is reporting a voltage higher than expected. In simple terms, the sensor that monitors the catalytic converter’s temperature is reading abnormally high values, suggesting a possible sensor fault, wiring issue, or exhaust overheating.

Affected Models: Porsche Macan, 991.1 Carrera, Cayenne, and other OBD-II equipped vehicles.

⚙️ What Causes Code P0428?

• Faulty catalyst temperature sensor (Bank 1)
• Short circuit in the sensor wiring (signal wire grounded or 5V short)
• Exhaust overheating due to rich fuel mixture
• Faulty Engine Control Module (rare)

💡 Tip: This code is often seen along with P0425–P0429 when there are sensor or wiring issues near the catalytic converter.

🚨 Symptoms of P0428

• Check Engine Light (CEL) illuminated
• Reduced engine performance
• Strong exhaust smell
• Possible overheating of catalytic converter
• Poor fuel efficiency

🧰 How to Diagnose and Fix Code P0428

Step 1 – Read and Confirm the Code

Use a professional OBD2 scanner like iCarsoft CR MAX to confirm P0428 and check for related codes such as P0425, P0426, or P0430 that could indicate other catalyst temperature or efficiency issues.

Step 2 – Inspect the Sensor and Wiring

Locate the catalyst temperature sensor (Bank 1) — usually installed in or near the catalytic converter on the exhaust manifold side of cylinder bank 1. Inspect wiring for heat damage, melted insulation, or corrosion.

Step 3 – Measure Sensor Voltage

With the ignition ON (engine off), check the signal voltage at the sensor connector using a digital multimeter. Typical reading should be between 0.1–4.9V. If it’s stuck high (above 4.9V), there’s likely a short or failed sensor.

Step 4 – Replace the Sensor if Necessary

If wiring is intact and readings remain incorrect, replace the catalyst temperature sensor with a genuine or high-quality OEM replacement. Clear the code and recheck after a short test drive.

🧩 Recommended Tool: iCarsoft CR MAX BT

❓ FAQ – Common Questions About P0428

Q1: Is it safe to drive with code P0428?

You can drive short distances, but prolonged operation may damage the catalytic converter due to excessive heat.

Q2: Can I clean the sensor instead of replacing it?

Usually not effective. Once the temperature sensor is exposed to exhaust contamination or thermal failure, it must be replaced.

Q3: Does P0428 always mean the sensor is bad?

Not necessarily — check wiring and connectors first. A shorted harness can trigger the same fault.

📘 Related Articles

• P0420 Code on Honda Vehicles: The Only Guide You Need
• P0429 Code – Catalyst Temperature Sensor High (Bank 2)