1991 Infiniti Q45 transmission doesn't shift

Hi walther, Thank you for the donation. Possible causes for the problem are : 1. Incorrect inhibitor switch or control linkage adjustment. 2. Faulty shift solenoid "A". 3. Control valve. 4. Revolution sensor and speed sensor signal 5. Brake band. Here are the trouble codes retrieval procedures. DIAGNOSIS 1991 Infiniti Q45 NOTE: Warning light trouble code flashes are referred to as "Judgement Flicker" by manufacturer in code charts. 1 . Ensure engine is at normal operating temperature. With ignition switch in OFF position, move selector lever to "D" position. Turn trip odometer reset button counterclockwise and hold. Turn ignition switch to ON position. Diagnostic information display (located on instrument panel, left of speedometer) should change to A/T diagnosis mode. 2 . Move selector lever to "3" position and depress accelerator pedal to floor then release. Diagnostic information display will flash trouble code. See Fig. 40. NOTE: Diagnostic information display will flash "OK" if system is normal. Diagnostic code charts also include codes shown in Fig. 40. See appropriate wiring diagram for terminal and wire circuit identification.

Let me know what the code(s) is/are and we can proceed from there.

Hi KHLow2008,thank you very much for your prompt response.
I followed your instructions, the little window displayed "AT CHECK" but after releasing the accelerator pedal continue showing AT CHECK, it doesn't show me the codes, Am I doing something wrong?
Thank you very much,

Walther

Hi Whalter, You are welcomed. AT Check is a fault code by itself. It could be any of those listed in ths chart.