P0135 – Meaning, Causes, Symptoms, & Fixes

What Does Code P0135 Mean?

• P0135 definition: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
• Issue Severity: MODERATE – Extended driving with this code may cause internal engine damage.
• Repair Urgency: Get this code fixed as soon as possible to avoid rough running, potential damage, and excessive fuel consumption and emissions.
• Diagnosis: The heating element in this oxygen sensor is not functioning properly.

Heated oxygen sensors contain heating elements to get them up to operating temperature quickly, minimizing the amount of time spent in open-loop operation (a fixed rich mixture). Code P0135 occurs when the powertrain control module tests the upstream heated oxygen sensor’s heater circuit on Bank 1 and detects a short in the circuit or excessive resistance in the heater circuit.

P0135 Causes

There are many potential causes of code P0135.

• Faulty Pre-Catalyst oxygen sensor
• Faulty wiring/connections
• Short or open ground in the wiring
• Blown Fuse
• Engine coolant temperature sensor is not operating correctly
• Faulty Power Control Module

P0135 Symptoms

• Check Engine Light is on
• Decreased fuel economy
• Rough running engine

How Do I Fix Code P0135?

With an oxygen sensor fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0135?

P0135 can be caused by anything from a bad oxygen sensor to faulty wiring to a blown fuse. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0135 code.

Possible Repair Costs for P0135

For error code P0135, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

• Oxygen Sensor $200-$300
• Fuse $5
• Wiring repair/replacement $100-$1000

DIY Steps to Diagnose Code P0135

Engine code P0135 could be caused by a number of things, including a bad oxygen sensor, faulty wiring, or just a blown fuse. If you’d like to try to fix code P0135 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):

• FIXD
• Vehicle-specific repair manual
• Multimeter

STEP 1: DO A ROAD TEST.

Clear the fault codes with your FIXD sensor, then go for a drive to see if the problem comes back. If the Check Engine Light comes back on, continue to Step 2.

STEP 2: CHECK OXYGEN SENSOR VOLTAGE.

Check that the O2 sensor is getting battery voltage by using your multimeter. Consult your vehicle repair manual to locate the harness connector for the bank 1 sensor 1 O2 sensor. Disconnect the harness connector and turn the ignition to the “on” position (do not start the engine). Test the O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual. If no power is getting to the oxygen sensor, check the fuse associated with that circuit. 

STEP 3: CHECK ELECTRICAL CONNECTIONS.

Visually check the electrical connections, wire harness, and metal tabs inside terminals for any damages. If damage exists, repair it or replace the associated parts. They might be part of the O2 sensor, but could also be elsewhere in your car’s wiring. Return to step 1 to verify that the problem is fixed. If no damage is found, proceed to step 4.

STEP 4: CHECK ENGINE GROUND.

Consult your repair manual to find where the engine ground is located. Check for corrosion and loose connections. Fix these problems if they exist, then restart the diagnostic process to verify that the problem is fixed.

STEP 5: REPLACE THE OXYGEN SENSOR.

If all of these tests reveal no other problems, replace the bank 1 sensor 1 O2 sensor. If this doesn’t fix it, please take it to the nearest auto shop so that they may check other possible issues, including the Engine Control Module (ECM).

Common P0135 diagnosis mistakes

Replacing the oxygen sensor when the issues could actually lie in wiring/connections.

Still Need Help Fixing Code P0135?

If you’ve followed the steps above and are still experiencing check engine code P0135, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

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Fixed It But The Check Engine Light Is Still On?

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