top of page

Part 3 - How To Test It


The Procedure

The following guide should give a step-by-step guide to testing the Throttle Position Switch using the onboard diagnostics that came with LH2.4.

​

  1. Pull the bonnet release and open the bonnet by pinching the release mechanism and lifting the bonnet.

  2. At the back right of the engine bay (on a right-hand drive vehicle, at least) there is a small black plastic cover, under which is the diagnostic box. Remove the cover by squeezing the plastic tabs on both sides of the cover and wiggling it upwards.

  3. In the cover is a small plastic cylinder, pull this out from its cap and push it, metal end first, into socket number 2.

  4. Insert the key into the ignition and turn it to Key Position 2 (KP2). The warning lights should all illuminate, but the engine should not be running.

  5. Return to the diagnostic box and push the button twice. The official timing is greater than 1 second, but less than 3 seconds. A short pause should be left between each press. After a brief period, the LED should blink rapidly.

  6. With the LED blinking rapidly, turn the throttle bobbin from idle. The LED should immediately extinguish and begin flashing the diagnostic code '3-3-2'. If the LED continues to blink rapidly, there is a fault with the idle TPS. To save time here, it is recommended to push the throttle bobbin to the wide-open position.

  7. After the diagnostic code has flashed up, the LED should return to blinking rapidly. With the LED blinking rapidly again, slowly release the throttle bobbin a tad. The LED should extinguish immediately and begin flashing the code '3-3-3'; however, it is worth persevering a couple of times with the wide-open switch, as it can be quite marginal to activate.

  8. Finish the test by returning the key to Key Position 0 (KP0) and thus killing power to the diagnostics system. Replace the test plug into its cap, and replace the cover on top of the diagnostics box.


Notes

Here are some further notes on the tests found out either by personal experimentation or through forums at various points:

​

  • Turbo models may not have the wide-open TPS installed (presumably either a different fuel injection quantity regulation method or the mixture is just permanently set to run richer in the turbo ECUs).

  • For vehicles with both position switches installed, it will be possible to make both of them actuate, although the adjustment is somewhat marginal (but again, certainly possible).

  • For more in-depth checking, a multimeter can be used on its continuity setting. This can be used to probe either onto the back of the connector (achieved by peeling back the rubber boot from the connector) or onto the TPS module itself (by depressing the metal wire latch and removing the connector entirely). The latter is more difficult but can help distinguish a poor connection from a faulty switch or similar. The pinout is given in Part 1 of this article.

  • The throttle bobbin has a small block cast onto the rim of it. This hits against a pair of stops which dictate the range of movement of the throttle assembly. This block can also catch on the bobbin mounting bracket, however, which can hinder testing of the wide-open TPS.

  • Similarly to the above point, if testing on an automatic car, the action of the kickdown cable may also interfere with testing of the wide-open TPS.

  • Due to the differing construction of both the idle TPS and wide-open TPS, the idle TPS will emit a faint click when actuated; however, the wide-open TPS will not emit any click when actuated. This does not necessarily mean that the wise-open TPS is faulty and the only way to check it properly is with a multimeter.

​

​

​

bottom of page