Q&A for How to Read and Understand OBD Codes

Search the code on the internet. This can help you figure out the meaning of the code, along with possible causes and solutions.

Check under the dash on the driver's side! This is where most OBDII ports are located.

An OBD device is better known as OBDII scan tool, which helps pull codes using the OBDII port on a vehicle.

OBDII is the newest communication protocol for vehicles. The older version was OBD, which was replaced between 1994 and 1996.

Inline engines like most four cylinders only have bank one, no bank two. An inline 6 (rare these days) may have two banks: bank one in front, bank two in the rear. On a V6, typically bank one is the side of a V-6 engine whose connecting rod is first in line on the crankshaft. That's hard to see on most engines. The banks really refer to the primary catalytic converters and their oxygen sensors. There is an O2 sensor before the cat. That one tunes or trims the engine's fuel/air ratio to minimize polluting emissions. There is also one after the cat. This one monitors the cat's efficiency.

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

A code P0446 could mean a faulty vent valve.

Ignition/Distributor Engine Speed Input Circuit Malfunction. Possible causes are faulty Ignition/Distributor engine speed sensor, faulty Crankshaft Position sensor Ignition/Distributor, engine speed sensor harness is open or shorted, Ignition/Distributor engine speed sensor circuit, poor electrical connection, low battery charge, faulty Engine Control Module (ECM).

Usually, p0420 is for a bad catalytic converter or front or rear O2 sensor; p0456 usually means you have an EVAP leak; and p0137 is for an O2 sensor as well.

Fault are DTC, diagnostic trouble codes. They have their own description so that the user can understand what is the problem in the car.

This code is usually triggered when a not registered or damaged key is used to start the engine. When the starting operation is carried out five or more times consecutively with the same unregistered key, the system will lock.

It means there is a short to voltage or ground on COP driver circuit.

No. It will read the same code once until you clear it after checking the said fault.

CAN is short for CAN bus. CAN is the low level, transport, protocol used to send messages. It's a signaling specification.

This means "Exhaust Gas Recirculation Sensor A Circuit High." Check your EGR valve. If it's old or doesn't rattle when you shake it, replace it and reset the code. If it's OK, replace the EGR Sensor.

Wheel speed tone performance. A possible causes are wheel bearing malfunction, deformation of the wheel speed detection encoder, adhesion of foreign materials on the wheel speed detection encoder, ABS-ECU malfunction, or the number of poles on the magnetic encoder for wheel speed detection (N-pole and S-pole) is changed.

The code reader can read zero codes if it was reset. Find a shop that you would trust to do the work if needed. I found one that will give me a free diagnostic reading. That is rare these days.

If your OBD scanner isn’t reading codes or the VIN after erasing them, it may be because erasing resets diagnostic monitors to a "not ready" status. The vehicle may need a complete drive cycle to generate new codes. Additionally, all pending codes are cleared when erased, so new codes will only appear if issues reoccur. Other causes include OBD scanner connection issues or low battery power affecting memory. Try unplugging the scanner, turning off the ignition, then reconnecting, or complete a drive cycle to refresh the system.

The "I/M Monitor Status" on an OBD screen shows the readiness of your vehicle’s emissions systems. Letters like "C," "EV," "O," "OH," and "E" indicate specific monitors: C (Catalyst), EV (Evaporative), O (Oxygen Sensor), OH (Oxygen Heater), and E (EGR System). Blinking means the monitor is still testing, while solid means it has passed and is ready. For emissions tests, all monitors should ideally be solid. If they keep blinking, driving under certain conditions may help complete the tests.

You’ll need a professional-grade scanner like the Autel IM608 or a Launch X431 device.

OBD scanners - regardless of company - will read your car's code(s) and return these error codes. These codes will be the same, despite a company change over two or more different brands. However, they may display the codes a little differently. You, however, may need to either look up what these codes mean, or it may read it out on screen.

If you see P069E on your vehicle, it may be a manufacturer-specific code rather than a standard OBD-II trouble code.

In the I/M Monitor Status of an OBD2 system, CAT stands for Catalytic Converter. It indicates whether the catalytic converter's performance has been monitored and if it's operating correctly. The monitor status helps determine if the catalytic converter has passed its diagnostic test and if it’s functioning properly to reduce emissions.

P1166 and P1167 typically indicate a problem with the Throttle Position Sensor (TPS) or its circuit, often related to voltage issues. P0102 is a Mass Air Flow (MAF) sensor circuit low code, suggesting a potential issue with the MAF sensor or its wiring. Possible faults include a faulty or misaligned TPS, a faulty MAF sensor, or wiring or connector issues affecting both sensors. Check the sensors, wiring, and connections for problems.

In OBD2 codes, "p/d" stands for "pending" or "permanent." Pending means the issue has been detected but hasn't yet triggered the check engine light, waiting for more occurrences. Permanent means the issue is logged as permanent and won't clear until resolved. In your case, P0016 p/d indicates a pending or permanent camshaft/crankshaft correlation error.

The terms EVS, CAT, and 025 on a Dodge Ram 1500 likely refer to important vehicle systems: 1. EVS (Evaporative Emissions System - EVAP): This system prevents fuel vapors from escaping into the atmosphere. Faults in the EVAP system, such as leaks, can trigger codes like P0440 or P0442. 2. CAT (Catalytic Converter): The catalytic converter reduces harmful emissions from the exhaust. Issues here can trigger codes like P0420 (catalyst efficiency below threshold). 3. 025 (Oxygen Sensor Bank 2 Sensor 1): This relates to the oxygen sensor on Bank 2 of the engine. It monitors the air-fuel mixture and can trigger codes like P025 or P0151 for sensor issues.

The message "PSG self test EEPROM" likely indicates that the Power Steering Control Module (PSG) is performing a self-test on its Electrically Erasable Programmable Read-Only Memory (EEPROM). This is a routine diagnostic procedure to check the functionality of the PSG.

You can use methods like vehicle history reports, physical inspection, maintenance records, diagnostic scans, odometer verification, and professional inspections to uncover any potential tampering or manipulation when buying a used car.

PSG stands for "Pressure Sensor Glow." When a diagnostic tool indicates "PSG self-test" on a lorry, it typically means that the system is performing a self-test on the pressure sensor for the glow plugs. Glow plugs are used in diesel engines to help with cold starts by heating the combustion chamber. The pressure sensor monitors the pressure in the combustion chamber during the glow plug cycle. If there's an issue with the glow plug system or pressure sensor, it could affect engine performance, especially during cold starts. It's advisable to have a qualified mechanic inspect the system to diagnose and address any underlying issues.

The red "ENG SYS" light in a Mitsubishi Fuso Canter 4p10 indicates a problem with the engine system. This could be due to engine malfunction, sensor failure, or other mechanical issues. It is recommended to have the vehicle inspected by a qualified mechanic to diagnose and address the specific issue causing the warning light to illuminate.