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GM 8.1L Engine P0131 and P0151 Fault: Intermittent Loss of Power and O2 Sensor Issues

Model: GM Fault Code: P0131 Posted: 2015-10-26 08:59

I own a Workhorse chassis motor home equipped with an 8.1L GM engine. I'm experiencing intermittent engine performance issues where the vehicle enters reduced power mode, triggering DTC codes P0131 and P0151. After stopping the vehicle and clearing the codes, the engine runs normally for many miles before the problem returns. I have already replaced the oxygen sensors, fuel filter, fuel pump, and thermostat (set to 180°F). Despite these repairs, the issue persists. I'm seeking advice on how to diagnose and resolve this recurring fault. Any insights into potential root causes or diagnostic steps would be greatly appreciated. Ed

Related fault codes
P0131P0151
Comments (5)
Anonymous 2015-10-26 11:39

A scan tool is essential—check all stored codes, review freeze frame data, examine fuel trims (FTs), and monitor the pre-cat O2 sensor voltages. Also verify for vacuum leaks.

Anonymous 2016-05-30 11:32

I have a 2004 Winnebago on a Workhorse chassis with P0131 and P0151 codes causing loss of power and engine light. I've replaced the O2 sensors, spark plugs, wires, fuel filter, and fuel pump—still experiencing the issue. After clearing the codes, the vehicle runs fine. I'm planning a long trip and need a reliable fix. Any suggestions from others?

Anonymous 2016-05-30 12:44

DTC P0131: HO2S Circuit Low Voltage - Bank 1 Sensor 1 DTC P0151: HO2S Circuit Low Voltage - Bank 2 Sensor 1 With a scan tool, check sensor voltages—possible causes include low voltage, stuck at fixed level, or open circuits. Also review MAP readings and fuel trims (FTs). No exhaust leaks detected. Without a scanner, initial steps should be: - Check fuel pressure - Inspect for vacuum leaks Using a digital multimeter (DVOM), probe the sensor's signal or return wire to check voltage. Then, enrich the air-fuel mixture—try spraying carb cleaner into the throttle body or partially covering it with a choke—to see if O2 sensor voltage responds. This can help determine if the sensor is functioning properly.

Anonymous 2016-08-10 23:22

I have a 2004 Bounder on a Workhorse chassis with repeated P0131 code detection. After replacing the Bank 1 O2 sensor, the engine ran well for miles before losing power again, accompanied by a popping noise and reappearing P0131. The issue seems to occur more frequently at high altitudes where air density is low and temperatures are hot. Could this be due to lean combustion? I’ve ruled out vacuum leaks—what could be causing the engine to run too lean? Any insights would be helpful.

Anonymous 2016-08-11 08:16

Use a scan tool to check the actual sensor voltage. Can you manually enrich the mixture (e.g., by spraying carb cleaner or partially covering the throttle body) and observe if the O2 sensor voltage changes? Also review fuel trims and freeze frame data for clues about lean conditions.