Last updated: 2025-10-15
Author: Mike – Porsche DIY Enthusiast since 2012
🔍 What Does Code P0429 Mean?
P0429 indicates that the catalyst temperature sensor (Bank 2) is sending a voltage signal higher than the expected range. This means the sensor is detecting an unusually high temperature or there’s an electrical issue such as a short to voltage.
Affected Models: Porsche Macan, 991.1 Carrera, Cayenne, and other OBD-II compliant vehicles.
⚙️ What Causes Code P0429?
- Faulty catalyst temperature sensor (Bank 2)
- Short circuit to voltage in the sensor wiring
- Exhaust overheating due to a rich mixture or misfire
- Connector corrosion or thermal damage near catalytic converter
- ECM internal failure (rare)
💡 Tip: P0429 is often paired with P0428 or P0426 when multiple sensors share the same harness or ground circuit.
🚨 Symptoms of P0429
- Check Engine Light illuminated
- Loss of engine power
- Increased exhaust temperature
- Possible sulfur or burning smell
- Poor fuel economy
🧰 How to Diagnose and Fix Code P0429
Step 1 – Read and Confirm the Code
Connect an iCarsoft CR MAX scanner to verify P0429 and check for companion codes such as P0425–P0428 or P0430.
Step 2 – Inspect the Sensor and Wiring
Locate the catalyst temperature sensor (Bank 2) — typically mounted on or near the catalytic converter on the opposite cylinder bank from Bank 1. Look for melted wires, loose connectors, or signs of exhaust heat damage.
Step 3 – Measure Sensor Voltage
With ignition ON (engine OFF), test the signal voltage using a digital multimeter. Normal range: 0.1V–4.9V. If voltage is fixed above 4.9V, suspect a short to power or failed sensor element.
Step 4 – Replace the Sensor if Necessary
If all wiring checks out, replace the faulty Bank 2 catalyst temperature sensor and clear the codes using your scanner. Perform a short test drive to confirm that the fault does not return.
🧩 Recommended Tool: iCarsoft CR MAX
❓ FAQ – Common Questions About P0429
Q1: Is P0429 serious?
Yes. A high catalyst temperature signal can indicate potential overheating, which may damage the catalytic converter if ignored.
Q2: Can a bad O2 sensor cause P0429?
Indirectly, yes. If the upstream oxygen sensor causes the engine to run rich, it can overheat the catalyst and affect temperature sensor readings.
Q3: Do I need to replace both Bank 1 and Bank 2 sensors together?
Not necessarily. Replace only the faulty sensor unless both show identical abnormal readings or are aged equally.
