Generic OBDII P Code List: P0100-P0199

Learn the code definitions and the most common causes for Generic OBDII P Codes P0100-P0199

This post lists the most common trouble codes in the OBDII P Codes P0100-P0199 category. These are air/fuel ratio-related trouble codes. Start by reading the most common codes and causes and then refer to the code chart at the end of the post for official code definitions.

There are two types of OBDII trouble codes

Type 1 codes are the more important because they can cause quick and severe damage, while Type 2 codes are less important but cannot be ignored.

How to find your code definition

There are 141 100-series codes. There are several ways to find the code definition in the chart below.
1) Enter the trouble code in the search box. That’s the fastest way
2) If you’d like to scroll all the codes, change the Number of entries to show on the page in “Show Entries” box. Click NEXT or PREVIOUS at the bottom right of the table

1) P0101, P0102, P0103, P0104 MAF codes are very common codes

Carbon buildup in an electronic throttle body

These codes can be caused by an air leak in the air duct leading from the air filter box to the throttle body, a vacuum leak anywhere on the engine, carbon buildup in the throttle body, a faulty electrical connector at the mass air flow sensor, or a bad mass air flow sensor.

In my experience, the most common DIY mistake is to automatically replace the mass air flow sensor without any further checking. Before you replace any components, start by checking the condition of the air duct from the air filter box to the throttle body. Look for tears in the plastic/rubber snorkel. Any type of unmetered air leak can cause these codes.

Next check for carbon buildup in the electronic throttle body. This code can set if the computer detects a difference between the commanded amount of air entering the throttle body versus the amount of air measured by the mass air flow sensor. I’ve seen many mass air flow sensors replaced simply because of carbon buildup in the throttle body. This happens a lot on Nissan vehicles.

3) A P0130 – P0139 and  P-150-P0159 are common oxygen sensor codes

Screw-in type oxygen sensor

Sensor codes show up as either high or low voltage or slow

movement. The biggest DIYer mistake on these codes is automatically replacing the oxygen sensor without doing any testing. The vast majority of oxygen sensors returned as defective turn out to be perfectly good. In other words they were telling the truth. Here’s an example; An oxygen sensor can set a lean code if there is an exhaust leak. The exhaust leak causes the oxygen center to see a lean condition, but that doesn’t mean the sensor is bad.

2) P0105, P0106, P0107, P0107, and P0109 MAP codes are very common codes

The manifold absolute pressure sensor measures the difference between manifold vacuum and barometric pressure. The most common cause for these codes is a vacuum leak, corrosion in the MAP sensor connector, dirt in the barometric pressure port on the MAP, or a bad map sensor. Unlike a MAF sensor that can be cleaned, a map sensor cannot. If it’s faulty, it must be replaced.

3) A P0128 code is also very common

A P0128 code is usually caused by a stuck open thermostat. The ECM looks at the outside temperature, the engine coolant temperature and engine rpm. Based on those data points the ECM determines how long it should take for the engine to reach operating temperature. If the engine doesn’t reach the expected operating temperature within the calculated warm-up time it sets A P0128 code.

©, 2024 Rick Muscoplat