Toyota Camry Check Engine Light

This article will address the most common error or ‘fault’ codes that trigger the illumination of the ‘Check Engine Light’ on the four cylinder Camry.

All modern automobiles engines are managed by on-board computers commonly referred to as an Electronic Control Module (ECM) or Powertrain Control Module (PCM). The PCM encompasses control for both the engine and the transmission. Electrical inputs to the PCM are received through sensors located throughout the engine compartment, are subsequently processed (in milliseconds) and electrical signals (voltage) sent to electronically controlled valves and relays to make the engine behave in a predictable manner. When expected electrical input signals from the sensors are either not received, received fast enough or out of a voltage range, a fault code is generated and stored in the PCM. The driver/owner of the Camry is informed of the fault with the yellow Check Engine Light coming on. As other output sensors fail, the fault codes will accumulate in the PCM until the problem has been identified, fixed and the fault code(s) erased. In addition, failure of input control valves and relays (recipients of PCM instruction data via electrical current) will generate fault codes as well. When all of these engine control devices are working in harmony with the PCM, the fuel economy, emissions and overall driveability of the Camry perform at optimum levels.

There are generic and vehicles specific fault codes. Generic fault codes are codes that are common to all vehicles that are OBDII (On-board Diagnosis Version II) compliant with SAE (Society of Automotive Engineers) and Federal EPA standards. Vehicle specific codes are additional codes added by the auto manufacturer to address specific vehicle functions not common with other vehicle makes and models.

Ignition Coils

Fuel Injectors

Idle Air Control Valve

EVAP Vacuum Switching Valve

Vapor Pressure Sensor

Oxygen Sensor (02) – At least two.

Crankshaft Position Sensor

Camshaft Position Sensor

Air/Fuel Sensor (California Emission Cars – replaces one of the O2 sensors)

Engine Coolant Temperature Sensor

Intake Air Temperature Sensor

Throttle Position Sensor

Manifold Absolute Pressure Sensor

Vehicle Speed Sensor

Exhaust Gas Recirculation Valve Position Sensor

Power Steering Pressure Switch

Transaxle Sensors

The fault codes generated by the OBDII only point to a possible problem or set of problems that require attention. Identification of the specific cause, in the absence of some expensive analysis tools, may be a matter of component testing as well as trial and error. Some repair facilities, including dealerships, take the ‘shotgun’ approach – which is to replace every possible item that can cause the fault code to go on. Their focus is to avoid revisiting the problem and having to deal with you, the customer, more than once. In other words, why spend 2 hours identifying a problem requiring either a part cleaning or a $10 part replacement? However, some of these parts can be in the hundreds of dollars.

These are the most common faults I have encountered with the Camry with their remedy:

X = values 0 through 9.

1. P013X and/or P015X with P113X. The 02 sensor (Oxygen) or Air/Fuel sensor (California Emission Cars) has gone bad. O2 sensors are wear items and do not last forever. They usually go bad approaching 80,000 miles. Just buy a new one and replace it. They can’t be cleaned. Go a few months without replacement runs the risk of destroying the catalytic converter. When the ECM gets a weak or inconsistent signal from the upstream (before the catalytic convert) 02 sensor, the ECM will send an enrich fuel signal command to the fuel injectors to protect the engine from overheating from an over lean air/fuel mixture. Fuel economy will significantly deteriorate. When the combustion exhaust gasses containing unburned fuel passes into the catalytic converter, the converter will overheat in the process of continuously burning combustible pollutants. In time the converter will burn out. When buying a new 02 or Air/Fuel sensor, get Denso or NGK. Bosch sensors and Hondas don’t see to get along and only last a couple of years with Toyotas. The warranty period for most electronic components is 90 days to 1 year.

2. P044X. Determine if your fuel cap is loose. If that doesn’t fix it, then it’s probably the VSV valve (part of the EVAP system) attached to the Charcoal canister has gone bad.

3. P030X. A spark plug or spark plug wire is bad. I’ve seen wires go bad from wire clips that have been broken off of their valve cover during spark plug replacement. The wire(s) then rest on the hot valve cover getting slowly destroyed by heat. In a worst case scenario, the check engine light will continuously blink. In such an event, the car should be serviced as soon as possible or the catalytic converter will go bad in short order. Multiple P030X or the ‘Random Cylinder Misfire’ code usually indicate a bad coil pack. Since coil packs are expensive, the ignition wires is a good starting point for replacement. Testing old ignition wires via the voltage resistance cannot be performed on new technology wires.

4. P0420. A bad downstream (after the catalytic converter) 02 sensor that monitors the efficiency of the catalytic converter -or- a bad catalytic converter. It is all guesswork In the absence of an exhaust analysis tool (like what they have at DMV) to determine the efficiency of the converter.

5. P0401 & P0402. This one can be a little tricky. Either the EGR (Exhaust Gas Recirculation) valve requires replacement or the VSV (Vacuum Switching Valve – EVAP system component) isn’t working properly. The replacement of the EGR valve (which isn’t cheap) may not resolve the problem unless the VSV valve is also replaced. The purpose of the EGR valve is to recycle a small amount of engine exhaust back into the air/fuel mixture to prevent the exhaust temperatures to rise to a level that will produce a pollutant called nitrogen oxide. The possible cheap solution: Mixing 4 ounces of Marvel Mystery Oil for every 10 gallons of fuel after a few tank fill-ups may resolve the problem.

OBDII Code Readers have significantly come down in price compared to a few years ago. A basic reader to just extract and rest the code … around $30. For text description accompanying the code … around $50. Car dealers … around $50+ for each reading. Most automotive retail parts stores will download and reset the code(s) for you for free. Why have your own? Sometimes the fault codes are anomalies that once reset, will not come back on. If the codes quickly reappear, then some maintenance work is in order. Regardless, at least one trip to the dealership, repair shop or parts store was avoided. Another method of resetting fault codes without knowing what the codes were is to disconnect the car’s battery…if re-entering your car’s radio stations and anti-theft code isn’t a hassle.

ODBII standards was implemented in 1994 to replace ODBI. With no knowledge of ODBIII as a new standard in the horizon, and if you intend on owning a motor vehicle for a while, having your own reader would be like buying a wrench – nice to have but don’t need to use it all the time.

Once the fault codes have been identified through the reader, go on the internet to get the fault description with some possible solutions to investigate.