Check Engine Light/VSC & 4WD lights explained

[JuneBug]

Every time you start your RAV4, many of the warning lights on the instrument panel light up and then go out. This is part of a self-test to make sure that these important lights are functioning properly. But what happens when some of these lights DON'T turn off? What should you do if some of these lights come on while driving? Of course, in the case of the oil pressure or A/T Temp light you should stop the car before any serious damage is done. However, in the case of the Check Engine Light (CEL), there's no need to panic! The CEL is only telling you that the Engine Control Module (ECM) has detected a fault. It could be something simple, like a loose gas cap or it could be something more serious.

Generally speaking, there are 2 different groups of lights that show up. The first scenario is when the CEL, VSC, and 4WD (TRAC in 2WD models) lights come on. The second scenario is when you see the VSC, ABS, and BRAKE lights on. Sometimes the 4WD or TRAC lights also show up. So why do all these lights come on at the same time and what do they mean? Let's take a look at each of these scenarios:

1. CEL, VSC, and 4WD/TRAC (Check Engine Light, Vehicle Stability Control, and 4-Wheel Drive/Traction Control



The CEL indicates that the ECM has stored a diagnostic trouble code (DTC) and means something is not quite right in the engine. It could be any of a hundred different things such as a bad spark plug or coil causing a misfire to a bad oxygen (O2) sensor or yes, even a loose gas cap. Fortunately, the code can be read from the ECM with an OBDII tester and will usually point to the area of the problem and often to the specific part. But why would a CEL shut down the VSC or 4WD systems? Many of these features depend on the engine running at peak performance. The VSC for example, uses not only the braking system, but also controls the throttle to help get the RAV out of tricky situations. If the engine is not running right, the ECM shuts down those systems that would affected.

2. VSC, ABS (Antilock Braking System), BRAKE, and sometimes TRAC (skidding car icon)



This series of lights indicate a problem with the braking system. The BRAKE light by itself means either the parking brake is on or the brake fluid level is low in the reservoir. But when the BRAKE light is on with these other lights, it's an ABS failure of some sort. In the vast majority of cases, this is usually caused by a bad or dirty wheel speed sensor. These sensors look somewhat like a bolt with wires on one end. The speed sensors detect the wheel speeds and send appropriate signals to the skid control ECU. Speed sensor rotors have rows of alternating N and S magnetic poles, and their magnetic fields change as the rotors turn. The speed sensors detect those magnetic changes and send pulse signals to the skid control ECU.



The ECU monitors the wheel speeds through these pulse signals to control the ABS control system. But if there is snow/ice or mud on the sensor, it may not detect the pulse, and a code is set. HOWEVER, this code is not set in the ECM, it's set in the Skid Control ECU. Many code readers can't see these codes, because they're only designed to look for engine codes in the ECM. That's why a lot of people get frustrated when a mechanic or auto parts place tells them they have no codes even with 3 or 4 lights glowing on the dash! The wheel sensor isn't always the problem in this scenario--some owners have reported a problem with the brake pedal switch or a trailer wiring harness caused these lights to show up.

I went back through many of the old threads and compiled a listing of all the RAV4World users who reported these error lights. Out of the 41 users who had the first scenario with the CEL, 31% reported the cause as a bad or defective charcoal canister filter. A defective O2 or A/F sensor accounted for 24% of these reports. The infamous loose gas cap was attributed to 19% of the reports. As for the second scenario, I only found 8 reports and 63% of those turned out to be broken or defective wheel speed sensors. To view the listing which shows the user name, lights, codes, and eventual fix, download it here:

RAV4 Diagnostic Lights.pdf

Many thanks to fellow user RickL for compiling the list into a nice PDF for easy viewing.

Next, I'll show how to read and clear the diagnostic trouble codes with or without a code reader.

[JuneBug]

If you have a CEL showing, the best way to read the code is with a good quality OBDII code reader. This device plugs into the diagnostic port under the dash near the hood release. It will read and display the codes that are stored in the ECM--these codes relate to engine and emission control system performance. The format for these codes is a P followed by up to 4 digits. For example, a P0031 code indicates a problem with the Oxygen (A/F) Sensor Heater Control Circuit, while a P0500 shows a malfunction in the VSS (vehicle speed sensor). While it is possible to read the CEL codes using the jumper method, it will only show a 2-digit code that doesn't correspond to the equivalent P code. If you don't have a code reader, many auto parts stores will let you borrow one or read the codes for you free of charge.

However, if you have other warning lights showing without the CEL, most code readers can't display the codes because they are not stored in the ECM. But there is an easy way to read these codes by using the jumper method. All you need is a short piece of small gauge wire--speaker wire works fine, or even a paper clip bent into a U shape. With the ignition off, place the jumper wire across pins 4 and 13 of the diagnostic port.



Now turn the key to ON, but don't start the engine. With the smart key system, push the button twice with your foot OFF the brake pedal. The warning lights should now be flashing on the instrument cluster. A light that is flashing regularly means that particular system is normal. A coded flash indicates a problem. For example, if the ABS light flashes 3 times, pauses, then flashes 4 times, that would be code 34--a problem with the Left Rear Wheel Speed Sensor. This corresponds with a code C0215 which is how a code reader would show it. In Toyota's documentation, they will show this code as C0215/34. Each of the other lights may be flashing a related code. In this example, you may see the CRUISE light flashing a code 69. This code shows a brake system malfunction because of the ABS problem. When one system sets a code, it often causes a domino effect which will trigger similar codes in other systems. When the root problem is corrected and the codes cleared, all the related codes should go away as well. As mentioned before, a CEL will indicate a code from the ECM, which will display with a P prefix, such as P0441. If you have a code reader that can read DTC's in the other systems, they will show up with a different letter. The VSC and ABS codes are stored in the Skid Control ECU and use the C prefix, such as C0278/11 which indicates a problem with the ABS Solenoid Relay Circuit. Still other codes start with a U such as U0122 (Communication Stop from VSC to ECM) which would show up as a flashing 82 on the CRUISE light.

So now that you have corrected the problem, by tightening the gas cap or replacing the O2 sensor, how can the codes be cleared? With a code reader you can use its clear codes function. Without a code reader, many people disconnect the battery for 1-2 minutes. But there is an easier way that doesn't require tools and won't affect your radio settings. Next to the battery is a fuse box. Open it and look for a 20 amp fuse labeled "EFI MAIN" and a 10 amp fuse labeled "ETCS". Pull both these fuses and wait a minute or two and plug them back in. The ECM codes should now be cleared and the lights off.



However, this procedure only clears the ECM codes. If you have ABS/VSC codes and lights, even disconnecting the battery will not clear them. To clear these codes from the Skid Control ECU, take your jumper wire and re-connect it to pins 4 and 13 of the diagnostic port. Now, turn on the ignition and immediately tap the brake pedal 8 or more times. You have to tap the brake pedal just enough to flash the brake lights 8 times and it has to be done within 5 seconds. Turn off the key, remove the jumper, and the lights and codes should be gone.

For a comprehensive list of all the ECM "P" codes, download this PDF:

ES-63.pdf

For the ABS/VSC "C" codes, download this PDF:

BC-62.pdf

Here is a brief explanation of the OBD-II protocols, compliance, and connectors:

OBD-II Overview


This document is a work in progress, and I will be adding to it from time to time. Any suggestions on how to make it better will be greatly appreciated!

[mtgal]

It is my understanding the replacement of the charcoal canister is covered under the Federal Emissions Warranty > 8 / 80,000. Check your owner's manual. The codes are P043F, P043E, P2401, P2402, P2419. The TSB is dated 3-24-09. I am in the process of trying to get the local dealer to cover this. The problem is that after some time passes, more codes appear and in order to isolate these few, I have to have them read it right after the lights come back on after having been cleared. They are located in a different city, so it's not as easy as it sounds.

[groverblue]

From the documents listed, I can't tell what all the codes I have mean. Here are the codes I have:

CEL = 14, 93
VSC = 51 = Engine Control System Malfunction - Engine control system
4WD = 82
Cruise = 69

I was able to determine the VSC code from document BC-62.pdf, but not the others. Where can I find those?

[bsba253369]

the malfunction indicator light, the VSC and 4WD lights stays on at same time

[JuneBug]

Originally Posted by groverblue

From the documents listed, I can't tell what all the codes I have mean. Here are the codes I have:

CEL = 14, 93
VSC = 51 = Engine Control System Malfunction - Engine control system
4WD = 82
Cruise = 69

I was able to determine the VSC code from document BC-62.pdf, but not the others. Where can I find those?

With the exception of the 93 (I got 94), these are the same codes I got from a loose gas cap.

Cruise 69 is "Brake system malfunction."

[groverblue]

Originally Posted by junebug1701

With the exception of the 93 (I got 94), these are the same codes I got from a loose gas cap.

Cruise 69 is "Brake system malfunction."

I don't want to turn this into a help thread, but I took it to Autozone to get scanned and this is what they came up with:

P0300 - Random/Multiple Cylinder Misfire Detected
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0304 - Cylinder 4 Misfire Detected
P0305 - Cylinder 5 Misfire Detected
P0306 - Cylinder 6 Misfire Detected
P0354 - Ignition Coil "D" Primary/Secondary Circuit

[JuneBug]

Originally Posted by groverblue

I don't want to turn this into a help thread, but I took it to Autozone to get scanned and this is what they came up with:

P0300 - Random/Multiple Cylinder Misfire Detected
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0304 - Cylinder 4 Misfire Detected
P0305 - Cylinder 5 Misfire Detected
P0306 - Cylinder 6 Misfire Detected
P0354 - Ignition Coil "D" Primary/Secondary Circuit

Read this thread:

P0356 Code plus 7 other codes - (Might be a bad coil.) --2006 V6 61,000 miles

[BryanBBFan]

I have this situation described, with the CEL, VSC and TRAC lights on. Unfortunately, I have not been able to deal with it for quite a while. I just got the codes read, adn they were P0606, P0136 and P0136. The main point is that during the time the lights have been on, the engine performance has stayed the same. No performance loss at all. The gas mileage has stayed the same. The gas mileage has even gotten better since I put on new tires. I don't want to go on randomly replacing parts until the lights go away. How can I find out more details on these codes, especially the P0606. Thanks

[Carbon]

Do an advanced search in the 4.3 forums. Search for P0606 along with the others if you like.

Check Engine Light/VSC & 4WD lights explained
4.3 RAV4 Trouble Codes contain both of the codes that you typed.