GM Diagnostics & Trouble Codes

P2635 is Fuel Pump 'A' Low Flow / Performance — the GM fuel pump control module commanded a pressure and didn't get it. Covers the three GM field actions on...

P00B7 infers low coolant flow from a 68°F gap between two temperature sensors — nothing actually measures flow. On a cold engine both should agree, which separates a sensor fault...

P0722 means no output speed signal at all. GM bulletin 17-NA-147 splits the repair at a 2 March 2017 build date, and 18-NA-083 traces fourteen transmission codes to one misaligned...

P0401 means insufficient EGR flow — and GM bulletin 18-NA-089 recommends replacing the EGR cooler rather than the valve on higher-mileage 2016-18 Volt 1.5L, where no other EGR code is...

P0641 and P0651 are shared 5-volt reference circuit faults — which is why one bad sensor sets codes for several good ones. Unplug sensors one at a time until the...

P1868 isn't a fault — it's a maintenance reminder saying calculated transmission fluid life has reached 10% or less. Clearing the code doesn't reset the counter, which is why it...

On a Chevrolet, P1719 is an ABS base brake solenoid circuit fault — not the transmission code that dominates search results. Base braking still works, but ABS, traction and stability...

P1630 has two GM definitions — system voltage error, or theft deterrent learn mode active. Your symptom usually settles which in seconds, and grounds are the first check under either.

P160C means injector flow rate calibration data was never programmed into the glow plug control module — usually after a module was replaced. The fix is programming, not parts, and...

Almost everything you'll find about P1400 describes Ford's DPFE sensor — a part most GM vehicles don't have. The GM attribution is thin, and this page shows you how to...

P1514 means measured airflow is higher than the throttle position accounts for — so one of two independent sensors is wrong, or the plate isn't where the module thinks. Cleaning...

P1403 names solenoid 1 of GM's three-solenoid digital EGR valve. Carbon in the small orifices is the dominant cause — the solenoid is often electrically perfect and mechanically stuck.

P1380 means the engine module couldn't get rough road data from the ABS — without it, a pothole and a dead cylinder look identical. The fault is usually in the...

P1247 has two legitimate GM definitions — Injector 8 Control Circuit Shorted, and Turbo Boost Pressure Low. Two questions about your engine settle which one applies to your vehicle.

P1336 doesn't report a broken part — it reports that a required setup procedure was never performed, usually after module or engine work. And misfire codes stored alongside may be...

P1271 means the two sensors in your accelerator pedal disagree, so the module stops trusting the pedal entirely. It's the pedal assembly rather than the throttle body — and a...

P1258 means the engine got hot enough that the module cut fuel to cylinders to protect it. The rough running and lost power are the protection strategy working — and...

GM's bulletin on these Duramax injector output circuit codes says explicitly not to replace injectors — inspect the wiring at C107 or C118 instead. And how many codes are stored...

P1191 is unusual: it names the location. Air is entering the ducting between the MAF sensor and throttle body — and it's often a duct left unseated after routine service,...

P1132 and P1153 both mean the bank 2 upstream oxygen sensor isn't oscillating properly — but bank 2 isn't a side of the car, and a flat signal doesn't always...

P1106 is GM's MAP sensor intermittent high voltage code — and "intermittent" is the clue. A signal that spikes and recovers points at a connection, not a component.

P0506 is idle too low, P0507 too high — opposite searches. But GM links P0506 plus a misfire to a broken valve spring, and on turbo crossovers the charge air...

P015B measures how fast the sensor responds, not what it reads — so a clogged injector or weak fuel pump can cause it with a perfectly accurate sensor. And a...

U0100 isn't stored by the ECM — it's other modules saying they can't hear it. GM's documented causes are grounds and connectors, including one ruined by the car's own sound-deadening...

GM's bulletins point P0340 and P0341 at harness chafing and corrosion at the X154 connector on 2014-2019 trucks — not the sensor. And P0016 alongside moves the diagnosis to timing...

P219A compares cylinders against each other, which rules out every shared component. GM's own sequence starts by checking the oil for fuel dilution and puts the oxygen sensor last.

P0612 says the module's injector relay control function failed a self-test. Whether that's a cheap relay repair or an ECM replacement depends on whether your injector control is separate or...

P305D is a DC/DC converter code — and GM's own bulletin traces it to condensation from the wireless phone charging pad's cooling duct dripping onto the converter. The documented repair...

P0717 means the transmission module sees no input speed signal at all. On GM's 6L80/6L90 that sensor lives inside the transmission — and a wrong valve body or a failing...

P046C means the EGR valve didn't reach the position it was commanded to. On GM diesels that's usually carbon holding the valve — the sensor is reporting accurately, so replacing...

P0141 is the downstream O2 sensor heater circuit — the sensor that judges your catalytic converter. It blocks the catalyst monitor, so you can repair it and still fail a...

P0135 is a fault in the oxygen sensor's heater circuit, not its ability to read oxygen. On GM trucks a blown O2A or O2B fuse causes this exact code with...

P2135 drops GM vehicles into Reduced Engine Power when the two throttle position sensors disagree. GM's special coverage names this code — and its repair instruction says Hitachi units need...

P0700 is not a fault — it's the transmission module asking the engine module to turn on the light. The real code is stored in the TCM, and a basic...

P0446 on GM trucks is usually dust, not a failed part — the EVAP vent breathes from under the vehicle. GM has issued the same fix across three bulletin generations...

P0087 means commanded rail pressure was never reached. GM wrote two bulletins pushing back on injection pump replacement — one says do not fit a second pump, the other admits...

P0106 is often a cheap MAP sensor — but GM has three bulletins linking it, with P0300 and P0506, to a broken valve spring on V8 engines. Replacing the sensor...

P0335 means the module lost the crankshaft signal — a genuine do-not-drive code. On GM the relearn after replacement is mandatory, and three verified bulletins show harness chafing is often...

P0325 is rarely a quick sensor swap on a GM V8. The cause splits by engine generation — water in the valley on Gen III/IV, sub-harness chafing on Gen V...

P0128 is a stuck-open thermostat — but on GM vehicles it triggers fail-safe behaviour that kills the temperature gauge, A/C and cruise, and throws a Steering Assist Reduced warning. GM...

P0496 means vapour is flowing when the EVAP system should be sealed — usually a purge valve stuck open. A free two-minute vacuum test confirms it, and GM bulletin 17-NA-409...

P0101 means the airflow reading is implausible, not that the sensor failed. GM's bulletins point at casting flash in the airbox, a charge air duct that pops off the throttle...

P0445 is a short in the EVAP purge valve circuit. GM bulletin 21-NA-124 lists seven critical connections to check first and puts the purge valve fourth in the diagnostic order...

P0562 means System Voltage Low. GM bulletin 18-NA-161 names this code directly and lists four causes — none of them the alternator — with exact voltage drop limits of 100...

P1101 on a Chevy Malibu is usually the charge air tube popping off the throttle body — GM issued emission recall N192271200 over it — or a plugged PCV orifice...

P1011 on a Chevy Malibu means the intake camshaft actuator was not in its locked park position at start-up. GM Special Coverage 15824 ran 10 years / 120,000 miles on...

P0299 on a Chevy Trax means turbocharger underboost. GM bulletin PI1366 gives a two-minute wastegate preload test that tells you whether the turbo is actually the problem before you replace...