Vehicle Speed Sensor
 

My '94 Camry LE (V6) won't shift into overdrive and the code says the vehicle speed sensor and it's circuit is bad. I replaced the sensor (from Rock Auto) and everything was okay for about two weeks when the check engine light came on again and I got the same code reading. The wires from the connector look okay, but I don't have the equipment to test the sensor (there's a YouTube video on how to test it), so I'm tempted to just replace the sensor again with a Toyota OEM sensor (especially since I can get it for $125). The problem I see is that the leads from the connector go into a very thick wiring harness and I have a feeling that troubleshooting it would cost more than just trying another sensor. Any suggestions would be greatly appreciated? Thanks!

The code will trip if there is no speed sensor signal to ECU AND the Park/Neutral switch is off (not in Park or Neutral) AND the car is being driven.

You can test the speed sensor as follows:

Disconnect harness plug and remove sensor.

Orient the sensor to have the 3 electrical socket pins (wring plug has been disconnected) facing toward you and sensor lug with bolt hole that bolts sensor to trans oriented down. Pin orientation from left to right is 1-2-3.

Connect a 12V DC positive lead to pin 1 and the negative lead to pin 2.

Connect positive lead of voltmeter to pin 3 and negative to pin 2.

Rotate shaft gear either direction.

When rotating meter voltage should vary between 0 to 11V and do so 4 times per revolution. If not meeting this spec the sensor is bad.

However if the speedometer working OK then speed sensor is working OK.

Can do the following tests:

Find the ECU and 4 harness plugs going to it all located behind glove box.

Check for short between SP1 terminal pin of ecu body and chassis ground.

With the 4 ECU electrical female plugs facing you (and you looking at the rear of the wiring harness plugs plugged into ECU and the indentations (notches) on the wiring plug bodies are oriented up. The SP1 plug is on far right.

When looking at the rear of the SP1 harness plug, SP1 terminal pin is on the 2nd row terminals from the top. And 2nd to the farthest left terminal. Note the farthest left terminal should not have a pin inside it. Many terminals do not have pins. Might be a violet/yellow wire which goes from ECU to combination meter (dash meter).

Remove this harness plug and check for a short between the SP1 pin on the plug mounted on the computer (not on harness plug) and chassis ground. Continuity should be 1M ohm or more.

If not OK check for bad wiring and electrical plugs.

If OK on same ECU SP1 terminal pin above check for voltage between pin and chassis ground. Turn on ign key. Voltage should be 9-14V

If test not OK check for open circuits between wiring Box 3 and ECM.

If test OK, check for open wiring or plugs between Box 3 above and combination meter.

Box 3 is located up under the dash behind the instrument console.

Red/blue wire at speed sensor goes to Gauge fuse.

Purple wire at sensor may change to green/black to purple and light green to green at Box 3 then both go to combination meter.

Wow. Thanks !!