🚨 Diagnostic Profile
- Vehicle/Equipment Make: CADILLAC
- Technical Description: Injector Circuit Cylinder 6 Intermittent
P1237 is a Powertrain code monitored by the Engine Control Module (ECM) or Powertrain Control Module (PCM). This code indicates that the PCM has detected an intermittent electrical fault in the fuel injector driver circuit for cylinder number 6. The PCM controls injector operation by grounding the injector circuit through an internal driver, and it monitors the circuit for proper voltage and current feedback during each injection event. When the PCM sees an unexpected open circuit, short, or voltage spike on the cylinder 6 injector circuit — but only intermittently rather than continuously — it sets this code. This often correlates with occasional misfires, rough idle, or hesitation under load, especially when the fault condition is present. Because the issue is intermittent, it can be caused by a loose or corroded connector pin, a chafed wire harness rubbing against an engine bay component, a failing injector solenoid winding that is heat or vibration sensitive, or a marginal PCM driver stage. This condition may also trigger the Check Engine Light to flash during an active misfire event and could cause the engine to enter a protective limp-mode under severe conditions to prevent catalytic converter damage.
🚨 Repair Difficulty Tier
- Difficulty Rating: Intermediate
This repair requires a digital multimeter and a capable scan tool with live data and injector balance/kV testing capability to catch the intermittent fault. A technician with moderate electrical diagnostic experience can perform this repair, but confirming an intermittent fault may take patience and a wiggle test procedure, making it more involved than a basic parts swap.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Visually inspect the cylinder 6 injector electrical connector for corrosion, bent pins, or a loose lock tab. Trace the wiring harness from the connector back toward the engine harness and PCM connector, checking for chafing, heat damage, or pinch points near brackets, the intake manifold, or exhaust components. Check for any aftermarket wiring, previous repairs, or rodent damage along the harness run. - Step 2: Diagnostic Verification
Using a scan tool, monitor live data for cylinder 6 misfire counts and injector pulse width while performing a wiggle test on the harness and connector to try to replicate the intermittent fault. With the key off and connector disconnected, use a digital multimeter to check injector coil resistance (typically 11-18 ohms depending on injector type) and compare it to the other cylinders. Perform a voltage drop test on the power feed and ground/control circuits with the engine running to identify intermittent voltage dropout under load or vibration. - Step 3: Resolution & Reset Process
If the injector resistance is out of specification or inconsistent during the wiggle test, replace the cylinder 6 fuel injector. If the injector tests good but the harness shows damage or a bad connection, repair or replace the affected section of wiring harness and connector, using proper weatherproof splices and dielectric grease. After the repair, clear the stored diagnostic trouble codes with the scan tool, then perform a test drive while monitoring live misfire and injector data to confirm the intermittent fault no longer returns.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Replacement fuel injector (if needed), wiring harness connector/pigtail repair kit, dielectric grease, scan tool with live data and misfire monitoring capability
- Average Component Price: $45 – $180 USD
- Estimated Labor Hours: 0.8 – 1.5 hours
- Total Estimated Budget: $130 – $330 USD