Damaged or chafed wiring harness between the ECM and cylinder 1 injector; Corroded or loose electrical connector at the cylinder 1 injector; Failed cylinder 1 fuel injector (open coil or shorted winding); Faulty engine control module (ECM) injector driver; Rodent damage or heat-related insulation breakdown on the injector circuit; Poor ground connection shared by the injector circuit

DTC codes / Jaguar codes / P1201

P1201 · JaguarCylinder 1 Injector Circuit Open/Shorted

Q: What does code P1201 mean?

Cylinder 1 Injector Circuit Open/Shorted. P1201 on a Jaguar means the engine control module (ECM) has detected an open circuit or a short to ground or power in the electrical path for cylinder 1's fuel injector. The ECM monitors the injector driver circuit and flags this code when the expected current flow or voltage signature falls outside the programmed limits.

P1201 on a Jaguar means the engine control module (ECM) has detected an open circuit or a short to ground or power in the electrical path for cylinder 1's fuel injector. The ECM monitors the injector driver circuit and flags this code when the expected current flow or voltage signature falls outside the programmed limits.

SystemPowertrain

Code typeJaguar specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or misfire felt as a shake or stumble, especially when cold
Noticeable loss of power and reduced fuel economy
Engine may run rich or lean depending on whether the circuit is open or shorted
In severe cases, the engine may enter limp mode or refuse to start
A strong raw fuel smell if the injector is stuck open due to a short

Common causes, most likely first

Damaged or chafed wiring harness between the ECM and cylinder 1 injector
Corroded or loose electrical connector at the cylinder 1 injector
Failed cylinder 1 fuel injector (open coil or shorted winding)
Faulty engine control module (ECM) injector driver
Rodent damage or heat-related insulation breakdown on the injector circuit
Poor ground connection shared by the injector circuit

How to diagnose and fix it

Scan all modules and record freeze-frame data to confirm P1201 is active and not historical
Inspect the cylinder 1 injector connector and harness for corrosion, chafing, or loose pins
Measure injector coil resistance with a multimeter and compare to the manufacturer's specification
Check for short to ground and short to power on the injector control wire with the ECM disconnected
Perform a voltage drop test on the injector power feed and ground circuit under load
Swap the cylinder 1 injector with a known-good one from another cylinder to see if the misfire moves
If the circuit and injector test good, test the ECM driver output with an oscilloscope or substitute a known-good ECM

Before you condemn the injector or ECM

A chafed harness behind the intake manifold or near the cam cover is a far more common cause on Jaguars than a failed injector itself, so always trace the full wire run before replacing parts.
The ECM driver can be damaged by a shorted injector, so if you replace the ECM without fixing the underlying injector or wiring fault, the new module will fail in the same way.
P1201 can be set intermittently by a connector that only loses contact when the engine is hot or vibrating, so a wiggle test of the harness while watching live misfire data is essential.
A stuck-open injector can hydrolock a cylinder and cause catastrophic engine damage, so do not ignore a strong fuel smell or a misfire that suddenly worsens.
Some Jaguar models use a shared power feed for multiple injectors; a fault in that feed can set P1201 alongside codes for other cylinders, so check for companion codes before assuming the fault is isolated to cylinder 1.

Can I keep driving with P1201?

You can drive a short distance to a repair shop if the engine runs smoothly and the check engine light is steady, but avoid hard acceleration and towing. If the engine misfires heavily, smells of raw fuel, or the light flashes, stop driving and have the vehicle towed to prevent catalytic converter damage or engine damage.

Tools that help

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