What this code means
P0202 may mean the PCM is detecting an electrical problem in the cylinder 2 fuel injector circuit.
What the vehicle may do
- The vehicle may run rough or misfire.
- The MIL can illuminate.
- The engine may have reduced power or uneven operation.
Possible fault areas
- Possible injector power supply circuit concern.
- Possible injector control circuit concern.
- Possible connector, terminal, or harness concern.
- Possible injector coil or mechanical pintle concern.
- Possible PCM driver concern after circuit checks are proven good.
Diagnostic path
Opening and fault logic
On this Ram 2500HD with the 6.4 HEMI gas engine, P0202 is a cylinder 2 fuel injector circuit open fault. In plain terms, the PCM may not be seeing the injector circuit behave the way it expects electrically. The truck may run rough, misfire, lose power, or turn the MIL on. The possible fault areas can include the injector power feed, the injector control side, connector or harness problems, the injector coil or pintle movement, and in some cases the PCM driver. The monitor runs when the ignition is on, battery voltage is above 10.9 volts, engine speed is below 3000 rpm, and the ASD/Main relay is powering the injector. The PCM is watching circuit continuity and the inductive spike from the injector coil. Anything that reduces maximum current flow or reduces that voltage spike can set this code.
Start with the basic checks and duplicate the fault
Start with the basic system checks before getting into pin tests. Then read and record all codes and captured operating data, and save a vehicle scan report in case you need it later. Look at the captured conditions, the monitor gates, and the set conditions. Clear the codes, then operate the vehicle or the system under those same conditions and try to make P0202 come back. If the code or symptom returns, continue into the injector circuit diagnosis. If it does not return, treat it like an intermittent. Check for related flash updates and service information before chasing the harness. If nothing applies, wiggle test the harness areas that carry this circuit while watching for the code to go active or scan data to change. If you scope it for an intermittent, a circuit high trigger is above 4.9 volts, and a circuit low trigger is below 0.1 volts. Before moving on, verify battery charge, battery operation, battery connections, related chassis grounds, and connector condition. Make sure the connectors are locked, and look closely for pushed out, corroded, spread, burnt, or broken terminals.
Set up the circuit diagnosis
Next, follow a structured diagnostic approach. Check for any service bulletins, Star On-line cases, or ECU flash updates that fit the code or symptom. Check for battery voltage codes in the ECU. Since this is a circuit code, handle circuit faults before chasing performance or rationality faults. At the injector, verify the connector is fully seated and locked before unplugging it. Then disconnect it and inspect for water intrusion, pushed out terminals, damaged terminals, corrosion, burn marks, or spread terminals.
Preferred lab scope path
The preferred path is the lab scope because it lets you look at the whole injector electrical path and can also show signs of a mechanically sticking pintle. Put channel A on the battery supply voltage circuit. Put channel B on the fuel injector control circuit. Put the channel C amp clamp on the battery supply voltage circuit. If it helps, run the same setup on another injector and keep that capture as a known-good comparison for current draw and inductive spike behavior. With the injector off, if battery voltage is not present on the control circuit, that points to a clear open in the path. If battery voltage is present on the supply circuit at the same time, that points toward an open injector coil. When the driver turns the injector on, the control circuit should be pulled near zero. If it is not, look for resistance in the control circuit path. If voltage drops low and then quickly ramps back toward battery voltage, the circuit may be drawing too much current and the driver may be shutting down for protection, or the low-side driver may be failing. Current should build to a peak of approximately 1.0 amp if the circuitry is good. The supply side should stay constant through the event; if supply voltage drops when the injector is energized, suspect resistance in the battery supply circuit. Any resistance found in either side can reduce current draw and reduce the inductive kick. And if the voltage ramps down smoothly without the pintle bump, that points to a stuck pintle inside the injector.
DVOM and load-test checks
If you are testing with a meter, load test the injector battery supply circuit with the recommended circuit load test tool or an equivalent tool. You can also probe the battery supply circuit with a 12-volt test light connected to ground. Back probe the injector supply circuit and monitor voltage at the injector. The supply should show constant battery voltage with the injector commanded on and off. If voltage drops when the injector is energized, there is resistance in that supply circuit. Then isolate the control circuit and check it for an open and for a short to ground with an ohmmeter. The control circuit can also be isolated and checked for resistance or short to ground with the load-test method. Measure injector coil resistance and compare it with the other injectors if technical data is not available. Fuel injector resistance is typically between 9.0 and 18.0 Ohms, and the difference should typically be less than 10% between injectors. Keep in mind that coil resistance only checks the injector electrically. It does not prove the injector is moving mechanically; that takes the scope pattern. If the scan tool has an actuator function for the driver circuit, back probe the injector control circuit while actuating the driver. You should see battery voltage when the driver is off, and no voltage on the control circuit when the driver is on.
PCM driver decision point
Do not jump to the PCM driver early. Check the battery supply circuit and the control circuit first. Only after both circuits check good should you evaluate the PCM driver. If those circuits are good and the control-circuit voltage is not cycling on and off during driver actuation, the PCM is most likely faulty.
Verify the repair
Keep verification separate from the testing. After repairs are complete, inspect the vehicle and make sure all engine components are properly installed and connected. Reassemble and reconnect anything that was disturbed, then clear all codes with the scan tool. If a component was removed or replaced, determine whether a learn procedure applies, and if that learn procedure is available in the scan tool, perform it before final verification. Skipping an available matching learn procedure can allow the same code, or another code, to set. If the PCM has been replaced, perform module programming, and make sure the secret key code, VIN, and odometer mileage are programmed after that. Then operate the vehicle under the repaired code’s monitor conditions and use the scan tool to confirm no codes have returned. If P0202 returns, check for applicable service bulletins or Star On-line cases, then go back through this diagnostic path instead of guessing. If the code and condition do not return, the repair is complete. The takeaway is simple: prove the feed, prove the control side, compare the injector electrically and with a scope when needed, and leave the PCM driver until the circuit has earned it. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often diagnosed by proving the injector feed, control circuit, injector behavior, and driver command in a structured order.
For more guided automotive diagnostics, visit STEP Diagnostics.
