Engine Controls - DTC P1507, P1540, P0500, AT Code 23

SOURCE: Subaru Tech Tips

TITLE: DTC P1507

APPLIES TO: 96-99 Legacy

SERVICE TIP:

If you have been dealing with a persistent P1507 code on the above vehicles and the code just won't go away even after replacement parts have been installed, check the negative battery cable for corrosion/poor contact. We suggest you do a voltage drop test between the negative battery cable and the intake manifold ground. Your reading should be '0' or very close to it. Typical information we get from the techs is that while driving, the speedometer will read fine but the speed signal to the ECU quits. VSP will read '0' on New Select Monitor for ECU but, reads fine on the TCU side. You'll most likely have output from the speedometer circuit to both the ECU and TCU also.

We also recommend you do the above check for codes P1540, P0500, AT code 23 or any combination of these codes.