Damaged or chafed wiring in the coil 2 primary feedback circuit, often near the coil connector or along the valve cover; Corroded, loose, or pushed-back terminals in the ignition coil 2 electrical connector; Failed ignition coil 2 with an open or shorted primary winding that corrupts the feedback signal; Faulty ignition control module (ICM) on engines that route coil feedback through it rather than directly to the PCM; PCM driver or feedback circuit fault, which is rare but occurs after water intrusion or a shorted coil; Poor engine ground or harness ground near the coil mounting point causing erratic feedback voltage

DTC codes / GM codes / P1305

P1305 · GMIgnition Coil 2 Primary Feedback Circuit

Q: What does code P1305 mean?

Ignition Coil 2 Primary Feedback Circuit. P1305 on a GM vehicle means the powertrain control module (PCM) has detected a fault in the primary feedback circuit for ignition coil number 2, which is the low-voltage signal the PCM uses to command and monitor that coil's firing. The PCM compares the expected coil primary current or voltage signature against what it actually sees and sets the code when the feedback does not match, indicating an open, short, or erratic circuit rather than a confirmed misfire.

P1305 on a GM vehicle means the powertrain control module (PCM) has detected a fault in the primary feedback circuit for ignition coil number 2, which is the low-voltage signal the PCM uses to command and monitor that coil's firing. The PCM compares the expected coil primary current or voltage signature against what it actually sees and sets the code when the feedback does not match, indicating an open, short, or erratic circuit rather than a confirmed misfire.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illuminated check engine light, often with no other symptoms besides the warning light
A noticeable engine misfire or rough idle, especially when the engine is cold or under light load
Slight hesitation or stumble during acceleration if coil 2 is not firing consistently
Reduced fuel economy and a faint raw-fuel smell from the exhaust if the misfire is ongoing
In some cases the PCM disables the coil driver and the engine runs on the remaining coils with a flashing check engine light

Common causes, most likely first

Damaged or chafed wiring in the coil 2 primary feedback circuit, often near the coil connector or along the valve cover
Corroded, loose, or pushed-back terminals in the ignition coil 2 electrical connector
Failed ignition coil 2 with an open or shorted primary winding that corrupts the feedback signal
Faulty ignition control module (ICM) on engines that route coil feedback through it rather than directly to the PCM
PCM driver or feedback circuit fault, which is rare but occurs after water intrusion or a shorted coil
Poor engine ground or harness ground near the coil mounting point causing erratic feedback voltage

How to diagnose and fix it

Inspect the ignition coil 2 connector and harness for corrosion, chafing, or pushed-back pins, and repair terminals as needed
Swap ignition coil 2 with a known-good coil from another cylinder and clear the code to see whether the fault follows the coil or stays with cylinder 2
Measure primary resistance of coil 2 and compare it to the manufacturer's specification and to a known-good coil
Back-probe the feedback circuit at the PCM and at the coil connector with a multimeter or oscilloscope to check for an open, short to ground, or short to voltage
Check the ignition control module and its connectors on engines that use one, since a failing module can distort the feedback signal
Verify engine and harness grounds are clean and tight, especially the ground near the coil mounting area
If all wiring and coils test good, diagnose the PCM driver circuit before condemning the PCM, as replacement requires programming

What the coil 2 feedback circuit really tells you

P1305 is a circuit feedback code, not a misfire code, so a coil that fires but sends a distorted feedback signal can set it without any driveability complaint.
Technicians often replace coil 2 immediately, but a chafed feedback wire near the coil connector is a more common cause on higher-mileage GM engines.
On some GM engines the ignition control module processes the coil feedback before the PCM sees it, so a failing module can set P1305 even when the coil and wiring test perfect.
A shorted coil 2 primary can damage the PCM driver if the code is ignored, turning a cheap coil replacement into an expensive module repair.
P1305 can appear alongside misfire codes for cylinder 2, but the absence of a misfire code does not rule out a coil feedback fault.

Can I keep driving with P1305?

You can usually drive a short distance to a repair shop if the engine runs smoothly, but avoid heavy acceleration and long trips because an ongoing misfire can overheat the catalytic converter. If the check engine light is flashing or the engine runs rough, stop driving and have the vehicle towed.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.