P0201
- Powertrain
- Generic (SAE)
- Emissions
Get it looked at now
A cylinder that is not being fuelled misfires, and the oxygen it pumps into the exhaust skews that bank's trims so the remaining cylinders run rich into an oxygen-loaded converter. A flashing check engine light means that converter is being damaged right now. A short to ground can also destroy the module's injector driver, adding a control unit to the repair.
- Safe to drive
- Drive only far enough to reach help, gently. If the check engine light is flashing, stop and have it towed.
Injector Circuit Malfunction — Cylinder 1
The computer detected a fault in the cylinder 1 injector circuit — most commonly an open: an open winding, or a break in the feed or control wire. Depending on the fault and the vehicle, the module may also shut that injector's driver down to protect its output stage, in which case cylinder 1 gets no fuel. Confirm whether the cylinder is actually dead — misfire counters, a stored P0301, or a current ramp — rather than assuming it.
The ECM switches injectors on their ground side and monitors current through the driver. It can distinguish an open load (no current when commanded), a short to ground (current flowing with the driver off) and a short to supply or a shorted winding (excessive current). P0201 is defined as Injector Circuit/Open for cylinder 1, and on most vehicles an open load is what sets it; a short to ground or to supply usually sets P0261 or P0262 instead. Some manufacturers do use P0201 for any cylinder 1 injector circuit fault, so read what else is stored before assuming which condition occurred. Port injectors are typically saturated designs with a coil in the region of 10 to 16 ohms; direct-injection and diesel injectors are driven far harder, with coils of only a couple of ohms fired from a boosted supply. The specific values are vehicle-specific.
How the car detected itDuring normal running the module pulses the injector and watches the current through its low-side driver. No current when commanded means an open winding, or an open in the feed or control wire. Current flowing when the driver is off means the control wire is shorted to ground. Excessive current means a shorted winding or a short to supply. Many modules disable the affected driver to protect the output stage, which is why the cylinder can go dead as soon as the code sets; others log the fault and keep commanding the injector, so verify the cylinder's contribution before assuming it is out.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Drive only far enough to reach help, gently. If the check engine light is flashing, stop and have it towed.
- Urgency
- Get it looked at now
- Will it pass emissions
- No
- If ignored
- The cylinder stays dead. The engine shakes, loses power and uses more fuel. The unfuelled cylinder pumps raw air into the exhaust, which skews that bank's fuel trims and drives excess fuel from the remaining cylinders into a converter already full of oxygen — that combination overheats and can destroy it, a repair often several times the cost of an injector. If the injector is firing intermittently rather than not at all, raw fuel goes down the pipe as well, which is worse. If the fault is a short to ground, the module's injector driver can be damaged permanently. A flashing light means that damage is happening as you drive.
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
These are the causes this code can have. For the order to work through them in, see what to check first.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Injector winding failed open | Very common | — |
| 2 | Wiring or connector fault | Common | — |
| 3 | ECU injector driver damaged | Occasional | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
In order. Each of these is cheaper or faster than what follows it, and each one can make the rest unnecessary.
Whether a misfire code for the same cylinder (P0301) is also stored
It confirms the cylinder is genuinely dead rather than the circuit fault being brief or intermittent, which changes how you test.
Which physical cylinder is number 1 on this specific engine
Numbering and layout conventions vary by manufacturer. Working on the wrong cylinder wastes the entire diagnosis.
The injector connector — unplug it and look for oil, corrosion, spread terminals or a cracked lock
Oil wicking into an injector connector is one of the most common real causes of this code and it costs nothing to find.
The harness where it runs along the valve cover or across hot components
Injector harnesses chafe on brackets and bake against hot surfaces. A wiring repair is far cheaper than any part.
Whether other injector circuit codes are stored at the same time
Multiple injector codes almost always point at a shared feed, ground, relay or module driver bank rather than at several failed injectors.
Confirm cylinder 1's position from the vehicle's own firing order and numbering
Tools Vehicle service information
Numbering conventions differ between manufacturers and between inline and V configurations. Establish the layout from service information rather than assuming the front of the engine or a particular side.
ExpectedCylinder 1 positively identified, along with which harness branch and module driver bank serve it.
Inspect and unplug the injector connector
Tools Hand tools, bright light, terminal test probe
Look for oil, fuel or coolant intrusion, green corrosion, melted plastic and spread terminals. Check terminal tension with a matching probe — a terminal that accepts a probe with no resistance has lost its grip and will cause an intermittent open.
ExpectedClean, dry, tight terminals and a connector that latches firmly with its seal intact.
Measure the injector coil resistance and compare it against the other injectors
Tools Digital multimeter
Measure at the injector itself, not through the harness. Then measure every other injector on the engine. Side-by-side comparison is diagnostically valid even without a published specification, which matters because that spec varies by vehicle.
ExpectedAll injectors within a narrow band of each other. An open reading, or a value well outside the group, identifies a failed winding.
Check for supply voltage at the injector where the design uses a battery feed
Tools Multimeter, low-current probe, vehicle wiring diagram
Most port-injection systems feed the injector from battery voltage and switch the ground at the module. Direct-injection and piezo diesel injectors are driven from a boosted supply instead — roughly 60-70 volts on GDI solenoid systems, 100-200 volts on piezo diesels. Treat it as a shock hazard: do not backprobe it live, and do not put a test light or an unprotected scope input across it. Use a low-current clamp around the wire instead.
ExpectedBattery voltage present on the feed side with the key on, on systems designed that way.
Check the control side for switching while cranking
Tools Noid light or oscilloscope
A noid light gives a quick yes or no; a scope shows the actual waveform and whether the pulse width is normal. No pulse with a good feed and a good coil moves the diagnosis to the control wire or the module driver.
ExpectedA steady, regular pulse matching the other injectors.
Current-ramp the injector with a low-amp probe
Tools Low-current probe and oscilloscope
This shows both electrical condition and mechanical behaviour at once. The pintle bump in the current waveform tells you the injector is actually opening, not just conducting.
ExpectedA normal current waveform with a visible pintle bump, matching the shape of the other injectors.
Voltage-drop and wiggle test the feed and control circuits back toward the module
Tools Multimeter, scan tool with recording
Test the feed and control paths under load rather than with a continuity check, and move the harness while recording data. Concentrate on where the loom passes brackets, the valve cover and any heat source. This is free and non-invasive, so it comes before anything that requires removing the rail.
ExpectedMinimal voltage drop and no change during the wiggle test. Any change localises the fault to that harness run.
Swap the suspect injector with one from another cylinder
Tools Hand tools, new injector seals and O-rings, seal sizing tool where required, scan tool with injector coding
Only once the feed and control circuits have tested clean under load does the swap become the remaining test. Fit new seals when you do it. On GDI and common-rail diesel engines, injectors carry calibration codes tied to a cylinder — update those codes in the module when you move them, or the swap creates its own fault and the result is meaningless. GDI Teflon combustion seals are single-use and require a sizing tool; diesel injectors need new copper washers and the specified clamp torque. If that tooling or coding capability is not available, prove the circuit electrically instead of swapping. Then clear codes and see which cylinder the fault reports against.
ExpectedIf the code moves to the new cylinder, the injector is at fault. If it stays with cylinder 1, the fault is in the wiring or the module driver.
| Repair | Only after you confirm | Typical cost | Who |
|---|---|---|---|
| Repair or replace the injector connector and terminals | Contamination, corrosion or lost terminal tension found, with the injector's own coil resistance measuring normal. | $100–$350 | DIY |
| Replace injector seals and O-rings | Required whenever the injector is removed, or hardened and damaged seals found during inspection. | $30–$220 | DIY |
| Replace the cylinder 1 fuel injector | Coil measures open or well outside the range of its neighbours, or the code follows the injector when swapped to another cylinder. | $150–$900 | DIY |
| Repair a chafed, broken or heat-damaged injector harness wire | Voltage drop, an open circuit, or a wiggle-test change isolating the fault to a section of harness. | $120–$450 | Hard |
| Repair a short to ground or to supply in the injector control circuit | Current flowing with the driver commanded off, or supply voltage present on the control wire with the injector unplugged. Note that on most vehicles these conditions set P0261 or P0262 rather than P0201. | $150–$600 | Hard |
| Repair or replace the engine control module | Injector, connector and wiring all verified good, but the driver still fails to switch the circuit. | $600–$1,800 | Shop |
US independent-shop ranges, parts and labour, excluding diagnostic time. Port injectors on an accessible rail sit at the low end. Direct-injection and diesel injectors cost far more, sometimes need special tools to extract, and on many diesels must be coded to the module after fitting.
- Replacing the injector before the circuit has been tested under load and the swap test run. The swap answers the question, but only where seals and any injector coding can be handled properly.
- Assuming cylinder 1 is at the front of the engine. It depends on the manufacturer's numbering, not on geography.
- Testing continuity instead of voltage drop on the feed and control circuits.
- Backprobing a live direct-injection or piezo diesel injector circuit. The boosted drive voltage is a shock hazard and will damage a test light or an unprotected scope input — measure it with a current clamp.
- Moving a GDI or common-rail diesel injector to another cylinder without transferring its calibration code in the module, which creates a fresh fault and makes the swap test meaningless.
- Ignoring a simultaneous misfire code that would confirm whether the cylinder is truly dead.
- Reusing injector seals and O-rings, which then leak fuel or let the injector draw air.
- Replacing the control module for a driver fault before proving the wiring is clean, since a short to ground in the harness will simply kill the new driver too.
- Fuel Injector
- Injector Wiring
- Ecu Injector Driver
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Reviewed
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