Code P1351 in 1997 Chevy Blazer: Ignition System Short Explained with DIY Fix

If you're experiencing a Code P1351 (Ignition Circuit High Voltage) on your 1997 Chevrolet Blazer with a 4.3L engine, this post provides a clear, step-by-step guide based on real-world troubleshooting. The P1351 code indicates an electrical short in the ignition system — commonly caused by worn components or faulty wiring. In my case, the vehicle would crank but fail to start intermittently, and sometimes would suddenly stall while driving. After diagnosing the issue, I found that a loose electrical connection at the fuel pump was responsible. When the ignition key was turned on, I didn’t hear the fuel pump activate — a sign of an interrupted power supply. The fuel pump had been replaced about a month earlier, and during installation, a hole was cut in the floorboard (under the back seat, behind the driver’s seat). To access it, simply fold down the rear seat and lift the carpet. I manually jiggled the wiring harness connected to the top of the fuel pump, and the vehicle started immediately. This confirmed that the issue was a loose or corroded connection. To further diagnose ignition problems: - Turn on the ignition without starting the engine. Listen for the fuel pump — if it doesn’t run, check the power supply to the fuel pump. - Remove a spark plug wire and place a metal clip about 1/4 inch away from a grounded metal surface. Crank the engine — you should see a visible spark. If not, proceed to the next step. - Remove the coil or distributor cap wire (which looks like a spark plug wire) and repeat the test. If no spark is observed at the spark plugs but there is spark at the distributor cap, replace the distributor cap. If you get spark at both locations, consider replacing the spark plugs — they may be weak due to moisture or contamination (flooded). If no spark is detected at the distributor cap, continue tracing the ignition wiring for shorts or damaged components. Note: Some users report that a 'MAP sensor' fault code is misdiagnosed. In two cases I’ve seen, replacing the MAP sensor did not resolve the issue — instead, replacing the EGR valve fixed it. This suggests that EGR-related issues can mimic MAP sensor faults in older Chevy Blazers. As a backyard mechanic, I find modern diagnostic codes frustrating — especially when they don’t provide clear, user-friendly messages. For example, instead of simply saying 'your gas cap is not tightly sealed,' vehicles now display complex error codes like P1351. This makes troubleshooting harder for average users. This guide is based on practical experience with 1997 Chevy Blazer owners facing similar issues. Always verify findings with a multimeter or professional tools when in doubt.