GM Diagnostics & Trouble Codes

A rough idle on a GM engine is usually the MAF or MAP, not the O2 sensor. Use this scan-data decision tree to work out which sensor to actually replace.

Gradual power loss is real, but the causes get ranked wrong almost everywhere. Restricted exhaust, airflow metering and a dragging brake cost far more than suspension or bearing drag —...

P0172 is "System Too Rich (Bank 1)" — the oxygen sensors report more fuel than the commanded air-fuel ratio. On the 2010–2017 Equinox 2.4L Ecotec, the usual cause is a...

P0191 is a fuel rail pressure sensor circuit range/performance fault. On the 2010–2017 Equinox 2.4L, a failing high-pressure fuel pump is the usual cause — including new aftermarket pumps that...

P0089 is "Fuel Pressure Regulator 1 Performance" — the engine control module is having to command the high-pressure fuel pump much harder, or much softer, than it expects in order...

P0011 is "A Camshaft Position — Timing Over-Advanced or System Performance (Bank 1)", the intake camshaft counterpart to P0014. On the 2010–2017 Equinox 2.4L Ecotec, low or dirty engine oil...

P0016 is a crankshaft-to-camshaft position correlation fault (Bank 1, Sensor A). Low or dirty oil and a failing cam or crank position sensor are common causes, and GM bulletin PIP5092F...

P228D is "Fuel Pressure Regulator 1 Control Performance — High Pressure." The engine control module compares the fuel rail pressure it asked for against what the fuel rail pressure sensor...

P0299 is "Turbocharger/Supercharger 'A' Underboost Condition" — the engine control module compared actual boost against the target it calculated and found actual boost falling short for long enough to set...

P0013 is "Exhaust Camshaft Position Actuator Solenoid Control Circuit." It is an electrical code, not a timing code — the engine control module has detected a fault in the wiring...

P1101 means the mass air flow sensor reading does not match what the ECM calculates from the MAP, EGR and throttle position sensors. On turbocharged Equinox models the usual causes...

P0014 is "Camshaft Position B — Timing Over-Advanced or System Performance, Bank 1." The exhaust camshaft is not where the engine control module wants it. On a Chevrolet Equinox the...

A dead coin-cell battery is the most common reason a Chevy Equinox key fob stops working, but worn buttons, water damage, signal interference, and a fob that's fallen out of...

Interior lights that stay on after every door is closed almost always trace back to a door jamb switch the body control module thinks is still open, though wiring damage...

A direct-injection Chevrolet Equinox has two fuel pressure sensors, not one — and a third sensor with a confusingly similar name that has nothing to do with either. The high-pressure...

Every Equinox dashboard uses a common language of colored warning lights — amber for non-critical issues that still need attention, and red for urgent problems that need action right away....

Code U01B0 means the vehicle's computer stopped receiving expected messages from the Battery Monitor Module (BMM) — a component that tracks your battery's state of charge and health to help...

GM's own bulletins tell technicians not to replace parts until the shutters are inspected and tested — and on the most documented platform, 16-NA-051 routes the repair by which connector...

U1510 always means a master module lost communication with a LIN bus device — but which module and which device changes by platform, and so does the repair. Ten verified...

Uconnect is a Stellantis system; GMC uses IntelliLink, Infotainment 3 and Google built-in. Knowing which you have decides which GM bulletin applies — and GM currently has an open document...

P0191 is Fuel Rail Pressure Sensor Performance. GM warns normal diagnostics can lead to unnecessary injection pump replacement; on 2017-2020 Duramax trucks the documented fix is often a $79 connector.

P1101 is Intake Air Flow System Performance. On GMC it is a 1.5L turbo Terrain issue with two documented causes, and 2019 Terrain owners have an open emission recall that...

P062F is control module long term memory performance. GM warns the same code can set in the transmission, engine or fuel pump module and the setting module must be identified...

No GM document covers P1516 on the GMC Terrain in any year. On the 2007-2011 Acadia 3.6L GM traces it to ice and oil deposits at the throttle body with...

P118B is a particulate matter sensor fault, not a DPF failure — and on 2016-2018 GM diesels there's a free emission recall covering an ECM software fault that stopped the...

GM states that Google built-in navigation will not work without an active data plan — and publishes a 20 to 30 second steering wheel reset it tells dealers to teach...

There's an important difference between a fob that's unresponsive (no functions work) and one that the vehicle simply doesn't recognize as authorized — often shown by a security warning light...

Most GMC key fob failures are the battery — but GM has documented a receiver that locks up and clears itself after five minutes, and a fob that drains because...

Your engine cooling fan kicks in when the engine gets hot enough (or when the AC is running) to pull additional air through the radiator, and a fan that won't...

When your fob's remote functions — lock, unlock, remote start — stop responding, the cause is usually simpler than a full fob replacement. A dying battery, a range or interference...

The Engine Control Module (ECM) is your GMC's main engine computer, managing fuel delivery, ignition timing, and countless sensor inputs. Genuine ECM failures are less common than owners often assume...

C0240 is not an ABS module fault. GM's wording is PCM Traction Control Not Allowed - the brake module reporting that the engine module lost the ability to reduce torque....

C0561 is an informational code meaning another module asked the brake module to disable stability control. GM's bulletin says do not replace the EBCM. Real sub-types, causes, parts and labor.

U1510 on a GMC Sierra means a master control module lost communication with a smart device on a LIN bus. GM's PIT5698D confirms LIN buses are not wired to the...

Code U1501 is a network communication code indicating a loss of communication between modules on the vehicle's data bus — specifically, an invalid or missing data message expected from another...

C056D is Electronic Control Unit Hardware, set by any of five modules. GM's rule is explicit: if stored only as history and not current, do not replace the module. On...

C0550 is Electronic Control Unit Performance. On 2007 and later GM full-size trucks it belongs to the suspension, PTO and transfer case modules, not the brake module - and GM...

GM's bulletins point at a two-sided pairing reset, a radio software update, and a set of behaviours GM classifies as normal design characteristics with an explicit instruction not to replace...

Code B1325 means a primary control module, typically the Body Control Module, detected system voltage falling below roughly 9 volts or spiking above roughly 18 volts on its power circuit....

Code B0229 relates to your GMC's HVAC recirculation door — the flap that controls whether the system pulls in fresh outside air or recirculates cabin air. This is an HVAC...

Code B1380 points to a fault in the ignition accessory circuit — the circuit that's active whenever the key is in the ACC or ON position and that powers many...

Code B3060 means the Theft Deterrent Module or Body Control Module received an unprogrammed transponder identification code from the key being used — in other words, the security system doesn't...

The myGMC app (and its remote start, lock, and vehicle status features) relies on a working connection between your phone, GMC's servers, and your vehicle's connected services module — and...

P1516 is a GM throttle actuator control code caused by carbon build-up. The repair has a second half people skip - the idle learn reset - and the special coverage...

P0449 is the EVAP vent solenoid circuit code. GM has documented three causes on late-model Silverado and Sierra trucks - dust intrusion, chassis harness damage and engine harness chafing -...

Code U1962 relates to Serial Data Authentication Configuration (SDAC) on GM's newer Vehicle Intelligence Platform, used on 2020-and-later Silverado, Sierra, Tahoe, Suburban, and Corvette models. It's a manufacturer-specific network security...

U0140 is Lost Communication With Body Control Module. GM traced one documented case to a ground nut left under-torqued at the factory, which set eleven codes across four modules. No...

U062F is widely published with the definition for P062F, a different code. GM's own descriptor is not public; the one GM bulletin naming U062F attributes it to a chafed engine...