When you are datalogging, you may notice that the fuel trims are quite different from the driver’s side bank (Bank 1) to the passenger side bank (Bank 2). This is an indication of a mechanical problem. We are unable to control fueling bank to bank, so we cannot purposefully make one side richer or leaner. Some of the causes of this can be:
- Front o2 sensors are crossed.. Meaning the passenger side is plugged into the drivers side o2 sensor and vice versa. See this link for more information.
- Bad o2 sensor heater fuse. Although, this will usually have a code accompanying it.
- Weak or dying o2 sensor. Not a bad idea to replace both at the same time.
- Vacuum leak. Pretty obvious, but vacuum leaks can cause a bank to bank split. We have found this smoke leak detector on amazon. It works great. This is an affiliate link if you decide to get one and want to help us out. https://amzn.to/4lYVpLk
- Exhaust leak. Very common. An exhaust leak before or after the sensor will draw in air by the venturi effect. A piece of paper can be held near questionable exhaust connections. If the paper is sucked up to the exhaust pipe than you are pulling air into the exhaust. This extra air will cause the o2 sensor to read differently.
- Ignition misfire. Misfires show up as lean.
- Valve train issues.
- Injector issue. This is the least common cause but it does happen. This seems to happen more often in GEN 5 Direct injected engines.
