GM Diagnostics & Trouble Codes

U0101 is Lost Communication With Transmission Control Module. GM lists nine causes and eight are wiring, terminals or connectors - and instructs technicians not to replace any module until the...

U0422 is Invalid Data Received From Body Control Module. GM tells technicians to ignore it in history absent U1534 or U1538, and never to replace the component named in an...

U1510 is a LIN bus communication code. GM's own bulletin warns seven other modules can set it, so it does not mean the grille shutter is bad. Causes, real part...

When turning the key produces absolutely nothing — no crank, no clicking, not even dashboard lights flickering — you're dealing with a specific, narrower set of possible causes than a...

"Won't start" covers a wide range of actual problems, and the fastest path to a fix is figuring out which category you're dealing with first: does the engine crank but...

A diagnostic trouble code (DTC) is your Chevy's way of telling you which system detected a problem and roughly what kind of problem it is, but a code is a...

A Cruze that blows cold, lukewarm, or inconsistent air almost always comes down to one of four systems: coolant level, the thermostat, the blend door actuator, or the blower motor...

StabiliTrak is GM's electronic stability control system, and a "Service StabiliTrak" message on your Cruze means the module has detected something it can't verify is working correctly — not necessarily...

Airbag warning light staying on, or wondering what a seatbelt pretensioner actually does? Here's how the SDM monitors your vehicle's restraint system and what to do when something's flagged.

Water dripping from the headliner or pooling on the floor after rain or a car wash? A clogged sunroof drain tube is one of the most common, most overlooked causes.

Your EV won't wake up even though the high-voltage battery shows plenty of range? That's a separate, smaller 12-volt battery problem — and it's more common than most EV owners...

Infotainment freezing, features not loading, or charging sessions behaving unpredictably on your Equinox EV or Blazer EV? Software issues have been a notable early theme on both.

A ticking noise from the engine bay that's louder when cold and quiets down as the engine warms up? A cracked exhaust manifold is one of the most common causes...

P0442 and P0455 are EVAP leak codes. GM's own bulletin lists seven critical connections, a four-step diagnostic order that puts the purge valve last, and the gas cap seventh —...

AC blowing warm air, or a loud clutch engagement noise from under the hood? Here's how to work through a no-cold-air complaint before assuming a full compressor replacement.

A rhythmic clicking or ticking from behind the dash, and air temperature that won't respond to your settings? That's the classic blend door actuator failure.

Blurry, black, delayed, or missing backup camera image? Here's how to work through the most common causes and when it's worth a camera upgrade.

Random dash lights, doors that lock themselves, or accessories that stop responding for no clear reason? The body control module may be the common thread.

Turn the key and get a click, silence, or nothing at all — but only sometimes? Here's how to tell starter motor failure apart from a battery or fuel problem.

Dimming lights, a battery warning light, or a dead battery that keeps coming back? Here's how to tell if your alternator is the problem.

Battery dead every morning even though the vehicle ran fine the night before? Here's how to find what's draining it while you're not driving.

A rhythmic clicking that only happens while turning is one of the most reliable diagnostic signs in the business. Here's what's wearing out and what it costs to fix.

A humming noise that changes when you weave the wheel is the classic wheel bearing symptom. Here's how to confirm it, and why waiting makes the repair more dangerous, not...

A vibration that gets worse with speed and comes from underneath the truck, not the steering wheel, usually points to the driveshaft. Here's how to confirm it.

A whine that changes pitch with speed almost always points to the differential. Here's how to tell gear wear from bearing failure before it gets expensive.

Rough restarts, delayed engagement, or a system that won't activate at all — here's what's actually going on with your GM vehicle's Auto Start-Stop system, and your real options.

A Malibu that stalls, shudders, or loses power without warning has a handful of well-documented causes. Here's how to work through them systematically.

A check engine light on a Camaro almost always traces back to one of a small handful of systems. Before you assume the worst, here's how to narrow it down...

A high-pitched whine from your turbocharged or Duramax diesel GM engine can range from completely normal turbo spool sound to an early warning sign of a failing component. Knowing the...

A squeal, grind, or clunk when you press the brake pedal is your car's way of telling you something needs attention before it becomes a safety issue. The type of...

A blank, blurry, or glitchy backup camera image is more than an inconvenience — it's a safety issue. GM rear cameras are generally reliable, but exposure to weather and road...

From the pump shutting off early to a check engine light right after fueling up, fuel system problems can show up at the worst times. Some issues are as simple...

A rattle, rumble, or hiss from underneath your GM truck or car usually points to a specific part of the exhaust system, and the type of noise you hear is...

A vibration that only shows up once you hit 55-70 mph is one of the more unsettling problems a driver can feel, and it's almost always tied to your wheels,...

A grinding, clicking, or clunking noise when you roll your window up or down is almost always mechanical rather than electrical, but the switch itself can also be the source...

OnStar not working in your GM? Work through the red light, the offline-after-battery-swap problem, app and hotspot failures, GM's N262547330 TCM update, and the 3G sunset on 2010-2018 vehicles.

Knock sensor codes on GM V8 trucks are extremely common — and in the vast majority of cases, the sensor itself isn't the problem. It's the wiring harness underneath the...

A stretched timing chain doesn't just make noise — it throws off cam timing enough to trigger correlation codes, misfires, and a real loss of power. Here's what drives the...

P0430 usually arrives with a converter quote attached. GM's own bulletin says do not replace any parts until the air filter housing is validated as sealed — sand bypassing the...

P0420 names the part that failed the test, not the part that caused it. GM's own bulletin says do not replace anything until the air filter housing is confirmed sealed...

P0521 might be a $30 sensor or an engine about to fail — and GM documented a third option most people miss: the oil filter fitted at the last service....

P1682 is rarely the ignition switch. GM names a specific failure point — terminal 51 in the underhood fuse block's X3 connector — and the repair can be a single...

P0171 means "System Too Lean, Bank 1" — the engine control module has been adding fuel to compensate for a mixture with too much air or too little fuel, and...

P1011 is about the intake cam actuator park lock solenoid — a start-up code, not a running one. It requires an overhead-cam engine, so the common pushrod V8 attribution appears...

P0014 appears on three different GM engine families and GM's guidance inverts between them — replace both solenoids on the 2.4L, but don't swap solenoids on the 3.6L V6. Also...

P0300 is a random misfire — but on modern GM V8s it usually means a collapsed AFM/DFM lifter. GM also published a bulletin saying the diagnostic sets this code falsely...

P06DD is named after a solenoid, but GM's bulletin identifies a timing chain tensioner spring wearing a hole through the oil pump. The fix is the tensioner guide — and...

P0741 stands for "Torque Converter Clutch Circuit Performance or Stuck Off" — the control module commanded the torque converter clutch to lock, watched input and output shaft speeds to confirm...