P0202: Injector Circuit/Open - Cylinder 2

An injector is switched by grounding it. Battery voltage sits waiting at one terminal, the module pulls the other down for a measured few milliseconds, and while it does so it checks that current actually flowed. P0202 means that check failed on the number two injector: the module commanded it and found no complete path to drive current through.

The first thing to take from that description is when the module can possibly know. It cannot detect an open circuit by sitting there — it only finds out at the instant it tries. This code is therefore set during running, at a specific engine speed and load, and that makes freeze frame more informative here than on most codes. Look at the rpm and load recorded at the moment it set. A fault captured at idle, with the engine barely working, points at a hard break — something is genuinely disconnected and would fail at any speed. A fault that only appears at higher rpm, under load, or after a long run points at something quite different: a connection that is intact when nothing is moving it and separates when heat and vibration do.

That second case is where money gets wasted, because of what happens next. The standard advice on injector codes is to measure the coil resistance and compare it with specification, and that advice is sound for a hard failure. It is close to useless for a thermal one. An injector winding is fine enamelled wire, and a winding that has cracked will sit closed at workshop temperature and separate once the engine bay is hot — expansion pulls the break apart. The same is true of a terminal that has lost its grip in the connector. So the sequence that catches people is: code sets on the motorway, car arrives at the workshop and cools down, resistance measures perfectly within specification, the wiring is declared good, the car is handed back, and the light comes on again on the way home. Nothing was missed through carelessness. The test simply asked the question at the wrong temperature.

The fix is to test in the state the fault lives in. Get the engine to full operating temperature and then check the circuit under load rather than statically — a voltage drop across the circuit while the injector is being pulsed, or a meter set to record minimum and maximum during a wiggle test on a hot engine. A circuit that is open only when hot will show itself, and a circuit that stays solid through that is genuinely healthy.

There is one more test on this code that costs nothing and settles a great deal, and it is more available here than on many engines because port-injection injectors sit on top of the intake where they can be reached without disturbing fuel under pressure. Swap the cylinder 2 injector with a neighbouring one and drive it. If the code moves to the other cylinder, the injector is at fault and you have proved it without buying anything. If the code stays on cylinder 2, the injector is innocent and the fault is in the harness, the connector or the module — and you have just saved yourself the cost of a part that would have changed nothing. On a direct-injection engine that swap is a much bigger job, since the injectors are sealed into the head with high-pressure lines, so weigh it accordingly.

Whatever the cause, a cylinder receiving no fuel sends its full charge of air into the exhaust. That is hard on the catalytic converter, and a flashing warning light means the damage is happening now rather than eventually.