Toyota Hilux Surf 1993 Owner's Manual page 274

EVALUATION
(a) If the measured values at all positions are higher than specified:
Throttle cable out of adjustment
Throttle valve defective
Regulator valve defective
(b) If the measured values at all positions are lower than specified:
Throttle cable out of adjustment
Throttle valve defective
Regulator valve defective
Oil pump defective
O/D direct clutch defective
(c) If pressure is low in the D position only:
D position circuit fluid leakage
Forward clutch defective
(d) If pressure is low in the R position only:
R position circuit fluid leakage
Direct clutch defective
First and reverse brake defective
AUTOMATIC TRANSMISSION – Troubleshooting (Mechanical System Tests)
AT–77