Infiniti F50. Manual - part 39

ON BOARD DIAGNOSTIC (OBD) SYSTEM

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 HOW TO ERASE DTC (NO TOOLS)

The A/T CHECK indicator lamp is located on the instrument panel.

1.

If the ignition switch stays “ON” after repair work, be sure to turn ignition switch “OFF” once. Wait at least
10 seconds and then turn it “ON” (engine stopped) again.

2.

Perform “TCM SELF-DIAGNOSTIC PROCEDURE (No Tools)”. Refer to 

AT-97, "TCM SELF-DIAGNOS-

TIC PROCEDURE (NO TOOLS)"

 . (The engine warm-up step can be skipped when performing the diag-

nosis only to erase the DTC.)

3.

Perform “OBD-II SELF-DIAGNOSTIC PROCEDURE (No tools)”. Refer to 

EC-64, "No Tools"

 .

Malfunction Indicator Lamp (MIL)

ECS00832

DESCRIPTION 

The MIL is located on the instrument panel.
1.

The MIL will light up when the ignition switch is turned “ON” with-
out the engine running. This is a bulb check.

●

If the MIL does not light up, refer to 

DI-33, "WARNING LAMPS"

 ,

or see 

EC-410, "DTC P0650 MIL"

 .

2.

When the engine is started, the MIL should go off.
If the MIL remains on, the on board diagnostic system has
detected an engine system malfunction.

SEF217U

AT-42

TROUBLE DIAGNOSIS

TROUBLE DIAGNOSIS

PFP:00004

DTC Inspection Priority Chart

ECS00833

If some DTCs are displayed at the same time, perform inspections one by one based on the following priority
chart.
NOTE:
If DTC U1000 is displayed with other DTCs, first perform the trouble diagnosis for DTC U1000. Refer to

AT-99

 .

Fail-Safe

ECS00834

The TCM has an electrical fail-safe mode. This mode makes it possible to operate even if there is a malfunc-
tion in a main electronic control input/output signal circuit. 
In fail-safe mode, even if the select lever is “D” or “M” mode, the transmission is fixed in 2nd, 4th, or 5th
(depending on the breakdown position), so the customer should feel “slipping” or “poor acceleration”. When
fail-safe mode is triggered, when the ignition switch is switched “ON”, the A/T CHECK indicator lamp flashes
for about 8 seconds. (Refer to 

AT-97, "TCM SELF-DIAGNOSTIC PROCEDURE (NO TOOLS)"

 ).

Even when the electronic circuits are normal, under special conditions (for example, when slamming on the
brake with the wheels spinning drastically and stopping the tire rotation), the transmission can go into fail-safe
mode. If this happens, switch “OFF” the ignition switch for 10 seconds, then switch it “ON” again to return to
the normal shift pattern. Also, the A/T CHECK indicator lamp flashes for about 8 seconds once, then is
cleared. Therefore, the customer's vehicle has returned to normal, so handle according to the “diagnostics
flow” (Refer to 

AT-45

 ).

FAIL-SAFE FUNCTION 

If any malfunction occurs in a sensor or solenoid, this function controls the A/T to make driving possible.

Vehicle Speed Sensor

●

Signals are input from two systems - from vehicle speed sensor A/T (revolution sensor) installed on the
transmission and from combination meter so normal driving is possible even if there is a malfunction in
one of the systems. And if vehicle speed sensor A/T (revolution sensor) has unusual cases, 5th gear and
manual mode are prohibited.

Accelerator Pedal Position Sensor

●

If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM accord-
ing to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow
systems, the engine speed is fixed by ECM to a pre-determined engine speed to make driving possible.

Throttle Position Sensor

●

If there is a malfunction in one of the systems, the accelerator opening angle is controlled by ECM accord-
ing to a pre-determined accelerator angle to make driving possible. And if there are malfunctions in tow
systems, the accelerator opening angle is controlled by the idle signal sent from the ECM which is based
on input indicating either idle condition or off-idle condition (pre-determined accelerator opening) in order
to make driving possible.

PNP Switch

●

In the unlikely event that a malfunction signal enters the TCM, the position indicator is switched “OFF”, the
starter relay is switched “OFF” (starter starting is disabled), and the position is fixed to the “D” range to
make driving possible.

PNP Relay

●

The PNP relay is switched “OFF”. (Starter starting is disabled.)

Priority

Detected items (DTC)

1

U1000 CAN communication line

2

Except above

TROUBLE DIAGNOSIS

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A/T Interlock

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If there is an A/T interlock judgment malfunction, the transmission is fixed in 2nd gear, 4th gear, or 5th
gear to make driving possible.
NOTE:
When the vehicle is driven fixed in 2nd gear or 5th gear, a turbine revolution sensor malfunction is
displayed, but this is not a turbine revolution sensor malfunction.

●

When the coupling pattern below is detected, the fail-safe action corresponding to the pattern is executed.

A/T INTERLOCK COUPLING PATTERN TABLE

●

: NG X: OK

A/T 1st Engine Braking

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When there is an A/T first gear engine brake judgment malfunction, the low coast brake solenoid is
switched “OFF” to avoid the engine brake operation.

Line Pressure Solenoid

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The solenoid is switched “OFF” and the line pressure is set to the maximum hydraulic pressure to make
driving possible.

Torque Converter Clutch Solenoid

●

The solenoid is switched “OFF” to release the lock-up.

Low Coast Brake Solenoid

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When a (electrical or functional) malfunction occurs, in order to make driving possible, if the solenoid is
“ON”, the transmission is held in 2nd gear; if the solenoid is “OFF”, the transmission is held in 4th gear.
(engine brake is not applied in 1st and 2nd gear.)

Input Clutch Solenoid

●

If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4th gear to make driving possible.

Direct Clutch Solenoid

●

If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4th gear to make driving possible.

Gear position

ATF pressure switch output

Fail-safe 

function

Clutch pressure output pattern after fail-safe func-

tion

SW3 

(I/C)

SW6 

(H&LR

/C)

SW5 

(D/C)

SW1 

(Fr/B)

SW2 

(LC/B)

I/C

H&LR/

C

D/C

Fr/B

LC/B

L/U

A/T inter-
lock cou-
pling pattern

1st

●

X

–

X

X

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

–

X

●

–

X

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

2nd

–

●

X

–

X

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

●

–

X

X

–

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

3rd

–

X

X

–

●

Held in 

2nd gear

OFF

OFF

ON

OFF

OFF

OFF

●

–

X

X

–

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

4th

–

X

X

–

●

Held in 

2nd gear

OFF

OFF

ON

OFF

OFF

OFF

X

–

X

●

–

Held in 5th 

gear

ON

ON

OFF

ON

OFF

OFF

5th

X

X

–

X

●

Held in 

2nd gear

OFF

OFF

ON

OFF

OFF

OFF

X

–

●

X

–

Held in 4th 

gear

ON

ON

ON

OFF

OFF

OFF

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TROUBLE DIAGNOSIS

Front Brake Clutch Solenoid

●

If a (electrical or functional) malfunction occurs with the solenoid “ON”, in order to make driving possible,
the A/T is held in 5th gear; if the solenoid is OFF, 4th gear.

High and Low Reverse Clutch Solenoid

●

If a (electrical or functional) malfunction occurs with the solenoid either “ON” or “OFF”, the transmission is
held in 4th gear to make driving possible.

Turbine Revolution Sensor 1 or 2

●

The control is the same as if there were no turbine revolution sensors, 5th gear and manual mode are pro-
hibited.

How To Perform Trouble Diagnosis For Quick and Accurate Repair

ECS00835

INTRODUCTION

The TCM receives a signal from the vehicle speed sensor, accelerator pedal position sensor (throttle position
sensor) or PNP switch and provides shift control or lock-up control via A/T solenoid valves.
The TCM also communicates with the ECM by means of a signal
sent from sensing elements used with the OBD-related parts of the
A/T system for malfunction-diagnostic purposes. The TCM is capa-
ble of diagnosing malfunctioning parts while the ECM can store mal-
functions in its memory.
Input and output signals must always be correct and stable in the
operation of the A/T system. The A/T system must be in good oper-
ating condition and be free of valve seizure, solenoid valve malfunc-
tion, etc.

It is much more difficult to diagnose an error that occurs intermit-
tently rather than continuously. Most intermittent errors are caused
by poor electric connections or improper wiring. In this case, careful
checking of suspected circuits may help prevent the replacement of
good parts.
A visual check only may not find the cause of the errors. A road test
with CONSULT-II (or GST) or a circuit tester connected should be
performed. Follow the 

AT-45, "WORK FLOW"

 .

Before undertaking actual checks, take a few minutes to talk with a
customer who approaches with a driveability complaint. The cus-
tomer can supply good information about such errors, especially
intermittent ones. Find out what symptoms are present and under
what conditions they occur. A “Diagnostic Worksheet” as shown on
the example (Refer to 

AT-46

 ) should be used.

Start your diagnosis by looking for “conventional” errors first. This will
help troubleshoot driveability errors on an electronically controlled
engine vehicle.
Also check related Service bulletins.

SAT631IB

SAT632I

SEF234G