Faulty fuel injector on cylinder 7 (open coil winding internally); Damaged or corroded electrical connector at the cylinder 7 injector; Broken or chafed wire in the injector harness near the cylinder 7 injector; Open circuit in the injector driver circuit inside the ECM (less common); Rodent damage to the injector wiring harness; Loose or backed-out terminal in the injector connector

DTC codes / Volkswagen codes / P1243

P1243 · VolkswagenCylinder 7 Injector Circuit Open Circuit

Q: What does code P1243 mean?

Cylinder 7 Injector Circuit Open Circuit. P1243 on a Volkswagen indicates the engine control module (ECM) has detected an open circuit in the electrical path for cylinder 7's fuel injector, meaning no current is flowing when the injector should be energized. This typically results in a misfire on cylinder 7 because that injector is not firing, and the ECM may disable the injector to protect the engine.

P1243 on a Volkswagen indicates the engine control module (ECM) has detected an open circuit in the electrical path for cylinder 7's fuel injector, meaning no current is flowing when the injector should be energized. This typically results in a misfire on cylinder 7 because that injector is not firing, and the ECM may disable the injector to protect the engine.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Rough idle or shaking, especially noticeable when the engine is cold or under load
Noticeable loss of power and reduced fuel economy
Engine misfire code (such as P0307) may be stored alongside P1243
Often no symptoms besides the warning light if the misfire is subtle at higher speeds
Possible smell of unburned fuel from the exhaust due to a non-firing injector
In some cases, the engine may enter limp mode to protect the catalytic converter

Common causes, most likely first

Faulty fuel injector on cylinder 7 (open coil winding internally)
Damaged or corroded electrical connector at the cylinder 7 injector
Broken or chafed wire in the injector harness near the cylinder 7 injector
Open circuit in the injector driver circuit inside the ECM (less common)
Rodent damage to the injector wiring harness
Loose or backed-out terminal in the injector connector

How to diagnose and fix it

Perform a visual inspection of the cylinder 7 injector connector and wiring for damage, corrosion, or looseness
Use a noid light or oscilloscope to check for a pulse signal at the cylinder 7 injector connector while cranking the engine
Measure the resistance of the cylinder 7 injector with a multimeter and compare to the manufacturer's specification (typically 10-15 ohms)
Check continuity of the injector circuit from the ECM connector to the injector connector to identify an open wire
If the injector resistance is out of spec or the coil is open, replace the cylinder 7 fuel injector
If the wiring is faulty, repair or replace the affected section of the harness
Clear the fault codes and verify the repair with a test drive, ensuring no misfire or pending codes return

Don't overlook the injector harness connector

A common mistake is replacing the injector without first checking the connector terminals, which often corrode or lose tension and cause an open circuit that mimics a failed injector.
The ECM may set P1243 without illuminating the check engine light immediately if the misfire is not severe enough to trigger the federal emissions threshold, so always scan for pending codes.
On some Volkswagen engines, the injector harness runs near hot components and can suffer heat damage that leads to intermittent open circuits, especially when the engine is cold.
P1243 can be set by a faulty ECM driver, but this is rare; always rule out the injector and wiring before condemning the ECM.
A noid light test is quick and definitive for confirming whether the ECM is commanding the injector, but it does not test the injector itself; combine it with a resistance check.

Can I keep driving with P1243?

You can drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because the misfire can overheat the catalytic converter and cause costly damage. If the engine is running very rough or flashing the check engine light, stop driving and have it towed.

Tools that help

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