How to Troubleshoot the TCS Light on a 2003 Honda Accord

by Don Bowman

The traction control system, or TCS, on a 2003 Honda Accord has several functions relative to maintaining constant tire speed and traction. It works in unison with the anti-lock braking system and the transmission to maintain this control. It receives signals from the wheel sensors, the transmission -- or its vehicle speed sensor -- and the ignition system to formulate its strategy. The strategy is to slow engine speed to reduce tire spin, reduce transmission gearing and apply the brake to the fastest spinning tire, or a combination of these.

Step 1

Open the hood and check to see if there are any fluid-related issues causing the TCS light to come on. Check the master brake cylinder fluid level and add brake fluid as needed. The master cylinder is located on the driver's side bulkhead (or firewall) and has a large circular tank behind it. Also check the transmission fluid level and add transmission fluid as necessary.

Step 2

Check the connections on the ABS brake modulator and module located directly in front of the master cylinder. The module is the computer portion of the ABS system. It is the notebook size component with a wiring harness connected to it in the immediate proximity of the modulator. It is easy to find the modulator by just following the brake lines from the master cylinder down to the modulator. Look for any corroded or disconnected wires.

Step 3

Look over the electrical connectors on the radiator side of the transmission for corrosion and disconnected or loose connectors. Check all the fuses in the fuse and relay box on the driver's side fender well and replace as necessary. Test-drive the vehicle and note any irregularities in the engine and transmission operation. Correct all problems with the engine and transmission for the TCS to work properly. If both the engine and transmission work properly, continue to the next step.

Step 4

Start the engine and check the dash lights for a check engine light. If the check engine light is on, the computer has set a code. Pull the codes to see if any of them are relevant to the TCS or ABS by plugging the diagnostic tool connector into the onboard diagnostics port under the driver's side of the dash.

Step 5

Turn the ignition key on (engine off). Turn the diagnostics scanner on. Follow the directions as the scanner prompts you for the description of the vehicle. Comply by inserting the information into the tool. After input of the initial information, the scanner displays several options from which to withdraw codes -- select the appropriate engine as listed. Press the "Read" button and the scanner begins to interrogate the onboard computer for codes in the designated area and display them on the screen. It will also provide a description of the problem and a method of monitoring it in operation for verification.

Step 6

Verify the fault code validity. The scanner, upon displaying a code, will give several options. It provides the method of operation, location on the vehicle, description and best test location of the connector, method of monitoring and what the signal should look like versus the defective one and finally, a way to check the item if there is no signal at all. Correct all coded problems before continuing.

Step 7

Set the scanner by selecting "Transmission" and press the "Read" button. Correct any problems found before continuing. Even if there is no code displayed concerning the vehicle speed sensor, it is still a good idea to monitor it in action to see if the signal may be present but irregular. Test-drive the car with the scanner connected and watch the VSS speed to see if it is consistent. If you find any irregularities, replace the VSS. If the signal from the VSS does not agree with the rear wheel sensors, all the signals are considered erroneous and not reliable so the computer rejects the signal.

Step 8

Verify the synchronization and signal existence in all four-wheel sensors. Place the scanner in the "ABS" mode. Select wheel sensor monitoring. Drive the car and watch the correlation among all four wheels. It will display a picture of each wheel and a speed beneath it. If one or more sensors appear to be malfunctioning, this is the problem. Replace any malfunctioning wheel sensors.

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