P0036 Code on a GMC: HO2S Heater Control Circuit, Bank 1 Sensor 2 (GMC Guide)

P0036 on a GMC is GM's "HO2S Heater Control Circuit, Bank 1 Sensor 2" — an electrical fault in the heater circuit of the oxygen sensor behind the catalytic converter on bank 1. It is not a sign that the sensor reads oxygen badly. On a Sierra, Yukon, Savana, Canyon, Acadia or Terrain it matters because a dead rear heater stops the catalyst and post-catalyst fuel trim tests from running, so the truck cannot pass a readiness check even when it drives perfectly. Two things surprised us. On the 2013–2015 GMC Acadia 3.6L, GM traced P0036 and a long list of other codes to one chafed harness and a blown fuse — no oxygen sensor needed. And GM's 2005 table for the older Gen III truck engines does not list P0036 at all: on those Sierras and Yukons the rear heater was judged under P0141.

What Does P0036 Mean on a GMC?

Every heated oxygen sensor (HO2S) has two parts in one body: a signal element that reports oxygen in the exhaust, and an electric heater that brings that element up to working temperature quickly. P0036 is about the heater only, and only for the downstream sensor on bank 1.

The heater is fed voltage through a fuse. The engine control module (ECM) completes the circuit to ground through a low-side driver, switching it on and off to hold the sensor at temperature. The ECM watches the voltage on that control wire to judge whether the circuit is healthy.

GM's 2017 OBD parameter table for group 03 — the file that covers the Sierra and Yukon 5.3L (L83) and 6.2L (L86), the Sierra 4.3L (LV3), the Savana 4.8L (L20), the Canyon 2.5L and 3.6L, the Acadia 2.5L and 3.6L and the Terrain 2.4L and 3.6L — defines P0036 like this:

• The ECM sees the control-circuit voltage outside its acceptable range while the driver is off, which indicates an open circuit. GM's threshold is about 200 kΩ or more between the signal and controller ground.
• The test runs continuously with the ignition in crank or run, voltage above 11 volts and the engine above 400 rpm.
• It needs 20 failures in 25 samples, at 250 milliseconds per sample.
• It is a Type B code — normally two failing trips before the check engine light turns on.
• GM notes that on certain controllers P0037 may set alongside it.

On 2007–2016 GMC trucks the same code also covers shorts (see below). So on a late-model GMC, P0036 points at an open somewhere in the heater path: a blown fuse, a broken or chafed wire, a loose or corroded terminal, a heater element burned open inside the sensor, or — last and rarest — the ECM driver. On a V6 or V8 GMC the bank 2 rear heater has its own code, P0056.

Which GMCs Set P0036

This code genuinely applies across the gasoline GMC range, but not all the way back. In GM's tables we confirmed P0036 for:

• Sierra, Yukon and Yukon XL Gen IV V8s — GM's 2007 table for the 5.3L (LY5 and LH6) truck engines and its 2012 truck group, which covers the 4.8L (L20), 5.3L (LC9, LMG), 6.2L (L9H) and 4.3L (LU3)
• Sierra, Yukon and Yukon XL Gen V engines — the 4.3L LV3, 5.3L L83/L84/L82 and 6.2L L86/L87 in GM's 2017 and 2019 tables
• Savana 4.3L, 4.8L and 6.0L vans
• Envoy 4.2L (LL8) and the 2004–2012 Canyon 3.7L (LLR) in GM's 2007 tables, and the current Canyon 2.5L and 3.6L
• Acadia 3.6L (LLT, later LGX) and 2.5L, and Terrain 2.4L and 3.6L

The Duramax diesels (2.8L, 3.0L and 6.6L) run a different emissions system and code set, and the Hummer EV has no exhaust at all, so this guide does not apply to them.

How GM's Definition Changed on GMC Trucks

The GMC truck tables show P0036 arriving and then narrowing over two decades:

• 2005 and earlier Gen III trucks. GM's 2005 table for the 4.3L (LU3), 4.8L (LR4), 5.3L (LM7, L59, L33), 6.0L (LQ4, LQ9) and 8.1L (L18) family has no P0036. The rear heater was checked under P0141 with a current monitor: heater current had to fall between about 0.25 and 3.125 amps. If you own an early-2000s Sierra or Yukon, the rear heater code you will see is P0141, not P0036.
• 2007 Gen IV trucks. GM's 2007 table for the 5.3L (LY5) truck lists P0036 as one code covering everything: voltage low with the driver open (short to ground or open circuit) or voltage high with the driver closed (short to voltage). The test ran between 9 and 18 volts above 400 rpm.
• 2012 truck group. Same broad definition — open, short to ground or short to voltage — with a wider 11–32 volt window, 20 failures in 25 samples.
• 2017 and later. P0036 is the open only. Short to ground is P0037 and short to voltage is P0038.

Where Bank 1 Sensor 2 Is on a GMC

"Sensor 2" is downstream, after the catalytic converter. "Sensor 1" is upstream. The front heater on the same bank is P0030, so check which code you actually have before ordering a part. "Bank 1" is the side of the engine with cylinder 1:

• Sierra, Yukon, Savana V8 and the 4.3L V6: bank 1 is the driver's side. The P0036 sensor sits in the driver-side pipe after that side's converter.
• Acadia and Terrain 3.6L (transverse): bank 1 is the rear bank, toward the firewall. That matches GM's Acadia bulletin, which places the bank 1 sensor harness at the back of the engine. The downstream sensor is usually reached from underneath.
• Canyon 3.6L (longitudinal): GM numbers the 3.6L's cylinder 1 bank as the right bank viewed from the flywheel end, which in a pickup is the passenger side. Trace the harness from the sensor before you buy.
• Four-cylinder Terrain, Acadia and Canyon: one bank; the rear sensor is the one after the converter.

The Acadia Harness Bulletin

GM bulletin PIT5336 (October 2014) covers the 2013–2015 GMC Acadia with the 3.6L (RPO LLT), along with the Buick Enclave and Chevrolet Traverse that share it. It is the single most useful GM document for a GMC owner with P0036.

The bulletin lists a long run of codes — P0030, P0031, P0032, P0036, P0037, P0038, the P0050–P0060 bank 2 heater codes, oxygen sensor signal codes such as P0131, P0137 and P0138, and purge solenoid code P0443 — and says the technician may also find the Emission 1 fuse open.

GM's finding: the engine harness to the bank 1 oxygen sensor can chafe on the A/C hose coupling at the back side of the engine. Once the insulation wears through, the circuit shorts, the shared fuse blows, and everything fed by that fuse loses power at once — which is why a whole family of codes shows up together.

The repair is wiring, not parts: repair the damaged circuits, insulate the harness, pull it away from the A/C hose coupling and tie-strap it to the main harness. The bulletin lists no part numbers, because the oxygen sensor is not the problem. If your Acadia has P0036 plus other oxygen sensor or purge codes, or the Emission 1 fuse keeps blowing, start here. A new fuse without the chafe repair will simply blow again.

A related GMC pattern: bulletin 24-NA-042 (April 2024) covers a misrouted Bank 1 Sensor 1 harness touching the exhaust on the 2024 Sierra 2500HD/3500HD 6.6L (L8T). It names front heater codes and P0137, not P0036 — but it shows how close GMC truck oxygen sensor wiring runs to the exhaust.

What P0036 Blocks

GM's tables group P0036 with P0137, P0138, P0140, P0141 and P0054 in the bank 1 sensor 2 fault bundle, and the downstream tests will not run while any of them is active. With P0036 set:

• Post-catalyst fuel trim (P2096 and P2097) cannot report — see our GMC P2096 guide.
• Catalyst efficiency (P0420) depends on a working rear sensor.
• Heater performance (P0141) is held off while a heater circuit code is active.

Symptoms of P0036

• Check engine light on
• Catalyst or oxygen sensor readiness monitors "not ready," which can fail an emissions inspection
• Usually no drivability change — the rear sensor does not run the main fuel mixture
• Several heater, oxygen sensor or purge codes at once if a shared fuse has blown (2013–2015 Acadia, PIT5336)
• Companion codes P0037, P0038, P0054 or P0141

Causes and How to Confirm Each

How Is P0036 Diagnosed on a GMC?

1. Record every code. Several heater, oxygen sensor and purge codes together on a 2013–2015 Acadia 3.6L point straight at PIT5336 and the Emission 1 fuse.
2. Identify the right sensor — bank 1, after the converter. Driver's side on a Sierra, Yukon or Savana V8; firewall side on a transverse 3.6L.
3. Check the fuse that feeds the heater. If it is open, find the short before installing a new one.
4. Unplug the sensor and check supply with a test lamp, key on.
5. Inspect the harness along its full run — on the Acadia, at the A/C hose coupling behind the engine; on a truck, wherever it passes the exhaust and frame.
6. Measure heater resistance across the sensor's heater pins. An open element confirms the sensor.
7. Test the control circuit back to the ECM for opens and, on older trucks, shorts.
8. Clear the codes and drive so the heater, catalyst and post-catalyst fuel trim monitors can complete.

Parts and Cost

GM Documents Relevant to P0036 on a GMC

PIT5336 is the only GM bulletin we found that names P0036 on a GMC. Have a dealer check your VIN against current bulletins rather than relying on any article, including this one.

What Other P0036 Pages Get Wrong

• "Replace the O2 sensor." GM's flow checks the fuse, supply and control circuit first. On the 2013–2015 Acadia the documented fix is a harness repair.
• Applying it to every GMC. GM's 2005 Gen III truck table has no P0036 — those Sierras and Yukons use P0141.
• Confusing Sensor 1 and Sensor 2. P0036 is the sensor after the converter. The front heater on the same bank is P0030.
• Replacing a blown fuse and moving on. On the Acadia, the reason it blew is documented — and it will blow again.

Frequently Asked Questions

Can I drive my GMC with P0036?

Generally yes in the short term. The rear sensor does not run the main fuel mixture, so drivability is usually unaffected. But the emissions monitors will not complete, and if a blown fuse is the cause, other components on that fuse may be without power too.

Is P0036 the front or rear oxygen sensor?

Rear: bank 1, after the catalytic converter. The front heater on the same bank sets P0030, and the bank 2 rear heater sets P0056.

Why does my Acadia have P0036 and a pile of other O2 codes?

GM's PIT5336 covers exactly this on the 2013–2015 Acadia 3.6L: the bank 1 O2 harness chafes on the A/C hose coupling at the back of the engine, shorts, and blows the Emission 1 fuse that feeds several components. Repair the harness, then the fuse.

Which side is bank 1 on a Sierra or Yukon?

The driver's side. The P0036 sensor is in the driver-side exhaust after that side's catalytic converter.

My 2003 Sierra has a rear heater fault but no P0036. Why?

GM's 2005 table for the Gen III truck engines does not use P0036. The rear heater on those trucks is monitored under P0141. See our P0141 guide.

Is there a Chevrolet version of this guide?

Yes. Our Chevrolet P0036 guide covers the Traverse side of the same PIT5336 bulletin.