🚨 Diagnostic Profile
- Vehicle/Equipment Make: CADILLAC
- Technical Description: Injector Circuit Cylinder 2 Intermittent
P1225 is a Powertrain-specific diagnostic trouble code monitored by the Engine Control Module (ECM) or Powertrain Control Module (PCM). This code indicates that the PCM has detected an intermittent electrical interruption in the fuel injector driver circuit for Cylinder 2. Unlike a continuous fault, an intermittent code means the PCM saw a momentary open circuit, short, or voltage irregularity in the injector control circuit — commonly caused by a loose connector, chafed wiring harness, a failing injector solenoid coil, or an unstable ground/power supply to the injector driver stage inside the PCM. Because the fault is intermittent, it may not be present at the time of testing, making it one of the more challenging driveability codes to pin down. Left unresolved, this can cause a random or cylinder-2-specific misfire, rough idle, hesitation under load, reduced fuel economy, and in some cases trigger the Check Engine Light to flash during active misfire events.
🚨 Repair Difficulty Tier
- Difficulty Rating: Intermediate
This repair requires a capable scan tool to pull freeze frame data and monitor injector pulse/short-term fuel trim data, along with a digital multimeter to check circuit resistance, voltage drop, and continuity on the injector harness. While the diagnostic process demands some technical know-how, a confident DIYer with proper tools can often trace and repair a wiring fault, whereas injector or PCM-level issues are best handled by a professional with access to OEM wiring diagrams.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin with a visual inspection of the Cylinder 2 fuel injector connector and wiring harness. Look for corrosion, melted insulation, loose or backed-out terminals, or chafing against engine components (valve covers, brackets, exhaust manifold heat shields). Wiggle-test the harness near the injector connector while watching for live data glitches on a scan tool, as intermittent faults are often connector-related. - Step 2: Diagnostic Verification
Using a scan tool, retrieve and record freeze frame data to identify the conditions (RPM, load, temperature) present when the code set. Back-probe the injector connector with a digital multimeter and check for correct reference voltage (typically battery voltage with key on) and verify the control circuit toggles properly when commanded. Measure resistance across the injector solenoid coil and compare it to OEM specification (commonly in the 11–16 ohm range for most GM port-injected engines) — an open or erratic reading confirms an internal injector fault rather than wiring. - Step 3: Resolution & Reset Process
If wiring is found to be damaged, repair or replace the affected harness section with proper weatherproof splice connectors and secure routing away from heat sources. If the injector itself tests out of specification or fails a resistance/activation test, replace the Cylinder 2 fuel injector using OEM or OEM-equivalent parts. After repair, clear the stored DTC with a scan tool, perform an injector balance test if available, and conduct a test drive under varied load conditions to confirm the code does not return.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: OEM-spec fuel injector, wiring harness repair kit/connector, digital multimeter, bi-directional scan tool with injector balance test capability
- Average Component Price: $45 – $180 USD (injector), $15 – $40 USD (harness repair kit)
- Estimated Labor Hours: 0.5 – 1.5 hours
- Total Estimated Budget: $100 – $350 USD depending on whether the fix is a simple wiring repair or full injector replacement