A 2002 Tacoma come into the shop with an intermittent no reverse, second gear starts and no shift to fourth gear. May or may not store code P0755. In this case the truck was scanned and a DTC P0755 for S2 solenoid performance was stored in memory. The code was recorded, then cleared and did not return even when the reverse and second gear start no fourth gear problem occurred during a road test.
The S2 solenoid was replaced and it was noticed that the pan was clean. A road test confirmed that intermittent problem of no reverse, second gear starts and no fourth was still present. A complete valve body assembly with different OE solenoids was also tried to no avail.
It was then decided to check voltage on the wires for the S1 and S2 solenoid to verify scan data and proper shift solenoid command. When functioning properly, at idle in Park, Neutral, Drive and Reverse, the S1 solenoid (violet wire) showed 12 volts and the S2 solenoid (light green wire) showed 0 volts. In forward ranges, S1 was ON (12 volts) in 1st and 2nd gears and OFF (0 voltage) in 3rd and 4th gear while S2 was ON (12 volts) in 2nd and 3rd gears and OFF (0 voltage) in 1st and 4th gears.
When the no reverse, 2nd gear start and no shift to 4th problem occurred, it was noticed that there was as little as 2 volts showing on the S2 solenoid’s light green wire when it should have been OFF (0 volts).
As a test, the S2 wire was cut. This caused reverse to engage immediately and also allowed for a first gear take off. Thinking there was a short to power somewhere in the circuit a new wire was run from the solenoid to the ECU connector. This isolated the wire from any external voltage intrusions. Unfortunately, the same problem remained with the 2 volt phantom showing up again. It was determined that the computer must have a bad driver so the shop bit the bullet and bought a new ECU. Of course I am sure you guessed, it didn’t fix the problem.
At this point there was nothing else to do but to go back over and check all grounds. In doing so, a loose bolt securing a gang of grounds was discovered in the engine compartment at the right front engine area (figures 1, 2 and 3). When the customer was quizzed he did say that the problem showed up after having engine work done at another garage. The customer might've saved themselves a lot of time and money if that little bit of information was made available to begin with.
Many thanks go to Ernie Garza from Victor Transmission for sharing this experience and pictures with us.
