On Board Diagnosis Logic

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by TCM as follows:

Torque converter slip ratio = A x C/B

Output shaft revolution signal from revolution sensor
Engine speed signal from ECM
Gear ratio determined as gear position which TCM supposes

If the actual gear position is much lower than the position (4th) supposed by TCM, the slip ratio will be much less than normal. In case the ratio does not reach the specified value, TCM judges this diagnosis malfunction.

This malfunction will be caused when shift solenoid valve B, line pressure solenoid valve are stuck closed and shift solenoid valve A is stuck open.

Fig 1: On Board Diagnosis Process

Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: DTC & Possible Cause Chart

Courtesy of NISSAN MOTOR CO., U.S.A.