← Back to list

2000 Ford Ranger 4.0L V6 with OBD2 Codes PO174, P115-1, PO306 and Cat Fault - Diagnosis & Repair Help

Model: 2000 Ford Ranger Fault Code: P1151 Posted: 2012-03-25 18:43

I'm experiencing a persistent issue with my 2000 Ford Ranger 4.0L V6 engine. Despite visiting three different repair shops—each of which charged an unreasonable fee—the problem continues. The vehicle has had repeated issues with cylinder #4, including oil leaks and a cracked porcelain base. Over the past two years, I've replaced the spark plug for cylinder #4 eight times due to porcelain failure. On one occasion, when the engine exhibited long-term fuel trim values of +13 on bank 2 and +9 on bank 1, replacing the spark plug restored normal readings. I have also completed the following repairs: new fuel injectors, new plenum gaskets, full replacement of all spark plugs and wires (twice), intake gasket replacements, two fuel filter changes, and a transmission flush. Additionally, I've performed coolant system flushes twice and replaced the thermostat. Currently, both cylinder #4 and cylinder #6 are showing issues. Before symptoms reappear, I notice a strong smell similar to hot radiator fluid. The radiator was inspected and no leaks were found; the overflow tank still contains water. The engine check light remains on, and OBD2 diagnostic codes PO174 (Fuel Trim Bank 2 Sensor 2), P1151 (O2 Sensor Bank 2 Sensor 1 - Slow Response), PO306 (Cylinder 6 Misfire Detected), and a catalytic converter fault are consistently appearing. I'm seeking expert advice on how to properly diagnose and resolve these issues, especially given the potential link between misfires and coolant leaks or head gasket failure.

Related fault codes
P1151
Comments (4)
Anonymous 2012-03-26 05:06

This question is a bit broad—could you clarify what repairs have already been performed? Have you searched existing forum discussions for these specific OBD2 codes on the 2000 Ford Ranger?

Anonymous 2012-04-04 12:06

Hello, and thank you for the detailed history. I've reviewed all the work done so far: new fuel injectors, plenum gaskets, spark plug replacement for cylinder #4 (eight times over two years), with one instance where long-term fuel trim improved after replacement. All spark plugs and wires were replaced twice. Intake gaskets have been replaced, fuel filters changed twice, valve covers show leaks—but I was told this wouldn't cause misfires. Injector flush completed, transmission flushed, cooling system flushed twice, thermostat replaced. Currently, cylinders #4 and #6 are problematic. A hot radiator smell appears before symptoms return. The radiator inspection showed no leaks, and the overflow tank still holds water. Repairs were done at three separate shops, including one from Ford. Any suggestions would be greatly appreciated.

Anonymous 2012-04-05 07:34

Misfires in adjacent cylinders combined with a hot coolant smell may indicate a head gasket failure. A leak-down test is recommended to confirm internal cylinder pressure and identify any leaks or combustion issues.

Anonymous 2012-04-05 08:02

Thanks for the suggestion—I'll perform a leak-down test soon. The smell I noticed was more like hot radiator fluid, not coolant—however, the radiator inspection came back clean with water in the overflow tank.