Nissan P0136 Downstream O2 Sensor Circuit: Fix

Fault-Code Fix

By iCarsoft Technical TeamJuly 3, 20266 min read

Check engine light on and a stored P0136? That’s the downstream oxygen sensor — bank 1, sensor 2, the one after the catalytic converter — or its circuit. The car usually still drives fine, but it won’t pass an emissions test until it’s fixed. Here’s how to confirm and repair it, with live data on an iCarsoft CR Max P.

Quick Answer

P0136 is a downstream O2 sensor (bank 1, sensor 2) circuit fault. Confirm the code, locate the sensor after the catalytic converter, check its wiring and connector, and look at the signal in live data. If the sensor is faulty, it unscrews and replaces — then clear the code and re-scan.

Key takeaways

P0136 = O2 sensor bank 1, sensor 2 (downstream / post-cat) circuit fault.
Most likely causes: the downstream sensor, its wiring/connector, or an exhaust leak.
Check it in live data — a healthy post-cat sensor holds a fairly steady voltage.
DIY-friendly — the sensor unscrews and replaces; clear the code and re-scan.

What P0136 means

P0136 is an oxygen (O2) sensor circuit fault for bank 1, sensor 2. Sensor 2 is the downstream sensor, fitted after the catalytic converter to monitor how well the cat is cleaning the exhaust. The code is a circuit fault — the ECU has seen an out-of-range or implausible signal from that sensor.

Where the sensor is

Bank 1 is the side of the engine with cylinder 1; sensor 2 is the one after the catalytic converter. On a four-cylinder engine there’s only one bank, so P0136 simply points to the post-cat oxygen sensor in the exhaust. As the video puts it, once you’ve confirmed the code, it’s down to the O2 sensor.

Symptoms

Check engine light on.
Usually no drivability change — the car runs normally.
Possible small drop in fuel economy.
Emissions test failure until repaired.

Common causes

Faulty downstream O2 sensor — the usual cause.
Wiring / connector at the sensor — damaged, corroded or loose.
Exhaust leak near the sensor skewing readings.
A heater-circuit fault inside the sensor; rarely the PCM.

Downstream oxygen (O2) sensor location after the catalytic converter on a Nissan — The downstream sensor sits after the cat — the video shows exactly which one.

Watch the fix

Video credit: Nissan P0136 O2s Downstream Circuit — How To Fix, by SA Diagnostic’s. Independent third-party demonstration.

Step-by-step fix

Plug in the iCarsoft CR Max P, scan and confirm P0136. Check the freeze-frame data.
Locate the downstream O2 sensor in the exhaust, after the catalytic converter.
Inspect the wiring and connector for damage, corrosion or a loose fit, and look for an exhaust leak near the sensor.
Check the sensor’s signal in live data (see below) to confirm it’s the fault.
Replace the O2 sensor if faulty — it unscrews with an O2 socket. Use an OEM-quality part and anti-seize on the threads.
Clear the codes and re-scan; confirm the reading is sensible and the code stays gone.

Verify with live data

Live data makes this an easy confirm. On the CR Max P, view the bank 1 sensor 2 voltage. With a healthy catalytic converter, the downstream sensor holds a fairly steady voltage (roughly 0.6–0.8 V) rather than switching rapidly like the upstream sensor. A reading that’s flat at zero, stuck, or jumping implausibly points to the sensor or its circuit. After fitting a new sensor, recheck live data, clear the code, and confirm it doesn’t return.

iCarsoft CR Max P showing the P0136 downstream O2 sensor code on a Nissan — Confirm P0136 first, then use live data to check the sensor 2 signal.

Downstream O2 sensor (bank 1 sensor 2) removed from a Nissan exhaust — The post-cat oxygen sensor unscrews with an O2 socket for replacement.

iCarsoft CR Max P — $599.99

Price at time of writing — check the product page for current pricing.

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Frequently asked questions

What does P0136 mean on a Nissan?

It’s an O2 sensor circuit fault for bank 1, sensor 2 — the downstream sensor after the catalytic converter. The ECU has seen an out-of-range or malfunctioning signal in that sensor’s circuit.

Where is the bank 1 sensor 2 O2 sensor?

It’s the downstream sensor, after the catalytic converter. Bank 1 is the side with cylinder 1; on a 4-cylinder there’s one bank, so it’s simply the post-cat sensor.

What are the symptoms of P0136?

Mostly a check engine light. The car usually drives normally, but you may see a small economy drop and it’ll fail an emissions test until fixed.

What causes a P0136 code?

Usually a failed downstream O2 sensor or its wiring/connector. An exhaust leak near the sensor or a heater-circuit fault can also cause it; rarely the PCM.

How do I test the downstream O2 sensor?

Use live data on the CR Max P: a healthy post-cat sensor holds a fairly steady voltage (about 0.6–0.8 V). A flat, stuck, or implausible reading points to the sensor or circuit.

Can I fix P0136 myself?

Usually yes — confirm the code, locate the sensor after the cat, inspect the wiring, check live data, and replace the sensor if faulty. It unscrews with an O2 socket.

Which iCarsoft tool is used?

The iCarsoft CR Max P ($599.99) — it reads/clears the code and streams O2 sensor live data to confirm the fault before you replace the sensor.

Disclaimer: Diagnostic and repair steps are general guidance — verify procedures and part numbers for your exact model and year. If you’re unsure, consult a qualified technician. The embedded video is an independent third-party demonstration. Prices are accurate at the time of writing.