Page 15 (Updated 02-Nov-2008)

Click To Page: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 INDEX
.
.
.

 

Engine & Transmission Computers:

1. ECU Engine Control Unit
2. TCU and Transmission Control System

.
.
.
Free Service Manual, Free Download.....see FAVORITE LINKS -page 26- FAVORITE LINKS
.
.
.

 

________________________________________________________________________________________________________________________

.
.

ECU Engine Control Unit

.
.

Location:

ECU is located below heater core unit, inside cabin, under plastic panel:
Left side is screw under plastic pop. Right side is plastic "screw" to be rotated 1/4 revolution which releases the underside plastic pin. Take cover off.
.
.
ECU and TCU Automatic Transmission Control Unit on Top.

ECU Program Selection lever, code led window.

 

ECU and TCU rear view; connectors beside gas pedal, plastic shield opened.

 

Starting related Inhibit Relay, plus some others are located under water reservoir beside the battery. See page 5

Note: For schematics see Favorite Links at page 26.
.
.

ECU power supply security relay to shield ECU from wrong polarized accidental connection, plus fuel pump relay. Trunk end panel is here opened.
Left: ECU pwr supply relay near batt, relay & IACV schema at right.

.
.
When doing diagnosis on these, be certain you know what you're probing -- hit the wrong terminal and you could fry the PCM.

ECU Connector pins:

ECU for VG30E (VE is 'about' same)connector pins and functions, compilated on one page. Read FSM EF&EC p.140.

Note: List for all ECU's is in Nissan TSB NTB93-167.pdf,
Connector installation: check Nissan TSB NTB94-065.pdf
.
.
.
SAFE MODE:

ECU has a Safe Mode -state when Camshaft (distributor) signal input fails, just like Automatic Transmission Control Unit TCU. In this state, engine rpm is limited to 2200rpm. Read FSM EF&EC 27.
.
.
.

TSB's see for http://maxima.theowensfamily.com/tsb
.
.
------------------------------------------------------------------------------------------------------------------------------------------
ECU Self diagnostics , click p.21
------------------------------------------------------------------------------------------------------------------------------------------
.
.
.
.
.

________________________________________________________________________________________________________________________

.
.

 

2. TCU Transmission Control Unit

VG30E type RE4F02A

____________________________________________________________

 

Transmission System Parts:
2b. Gear Lockup / Safe Mode
2c. Rev sensor, Solenoid pack, Inhibitor sw connectors
2d. Inhibitor switch
2e. Power / Comfort Mode Switch

 

____________________________________________________________

 

General Schematics , Updated 04/2008

.
.
.
Transmission testflow for electronics:
1. Test charge voltage at battery -> min 13.8V
2. Run Self Diagnostics
PREREQUISITES: Inhibitor sw is ok, Power/Comfort sw is ok, TPS is ok (see TPS page 6)
3. Check charge voltage/gnd at TCU -> min 12.5V
4. Test the main TCU connector pin voltages with DMM
5. Open solenoid connectors under hood, on tranny, measure solenoid etc. resistances.
.
.
.
Help for some Mechanical issues, Total A/T oil change see page 24

(Transmission for VE type RE4F04 is mechanically
lots different; TCU connectors 'about' the same.)
.
.
.
Note: The Maxima automatic transmission is GREAT! Some say it has a bad image of frequent breakdowns. My short experience tells that its a great box, breakdown might be possible via slipping like any other automatic. One major cause for slipping is the oxidized connections that starve the actuating hydraulic solenoids inside the tranny. I had this veeery soft gearchange which (I guess) could develop to slipping. After all connectors cleanup, all slipping vanished from my transmission.

Year 2008 Note: the 2nd gear now slips a little...

For TCU etc. connector cleanup refer to page14.
.
.
TCU connector pins and functions , compilated on one page.

.

.
.

Building a DIY TCU -Tester:

To easily reach those pins for testing during drive, I soldered a parallel connector with extension wire. Here its seen in the half way house, the TCU connector taken to passenger side for surgery... I had a downshift problem, twice a year from OD to 2nd didnt come through. For two years I watched the leds: no I know (2008) that electronically all signals work - some hydraylics now does not like playing... is it time for the upgrade?

.
.
.
Building a simple test cable using a screw terminal block:

View from drivers side, TCU connector white plastic shield has been removed. Here in this example, Power supply1 (+12V), TCU GROUND, and TPS signal are to be tested. (Backup Power supply2 is pin23).

Insert the test wires attached pins into TCU connector/signal(s) you're interested in, then attach multimeter probes into terminal block sockets, screw tight and go for a test drive...

At left, a paper clip has been pushed inside the TCU connector from rear. At right, three test wires attached to TCU connector: Pin4 = Power supply, Pin48 = TCU Ground, Pin35 = TPS signal.


.
.
.

_____________________________________________________________________

 

.
.
.

2b. Gear Lockup, Safe Mode, Shift Lock and Line Pressure drop Resistor - features

.
.
.
- GEAR LOCKUP : 3rd and 4th Gear lockup feature:
.
One of the nice features in this auto-gearbox is the direct lockup which is enabled over 50mph, warmed tranny, steady drive. At 3 or 4 gears, the gas guzzling turbine is 'bypassed' with direct mechanical lockup. The torque converter is locked via TCU signal to torque converter clutch solenoid.

I had problems with this lockup -feature, but connector cleanup cleared this problem also [vanished after tedious cleaning TCU connector with cleaner]. Went testing yesterday, 28F, tranny at 72F at startup: It took 20miles drive at 60mph to warm-up the tranny. After that the lockup performed perfectly.
.
.
How a working lockup is seen without measurements? While driving steady 60mph after 20minute drive, slight acceleration does not produce rpm needle to jump, but rpm response is equal to manual transmission. If you accelerate more, then the lockup disengages and rpm's jump like in 'normal' A/T driving.

This gearlock utilization results in 10% less fuel consumption. Notice that it needs up to 20 miles drive first to become functional [tranny temp up], and that starting from garage!

See FSM p. AT-72.
.
.
.
- SAFE MODE (see FSM AT-25):
The A/T has an inbuilt fail safe mode. In this mode the vehicle runs in third gear and will not up/down-shift, sluggish, poor accel. This safety feature may activate if during hard brake A/T is accidentally dropped to N, sensor failure or for some other reason. Stop engine, restart. If problem persists, check: Speed sensor, Revolution sensor...

Here is an 2008 -example how failing speed sensor intermittently drops 2001 Maxima SE A/T, (115kmiles) into SAFE MODE, by zoemayne: "...it was the speed sensor (rev sensor) which is located behind the drivers wheel/shock. $170 dealer part..."
Video Link http://www.youtube.com/watch?v=OMJQY9UQfLI
Forum Link www.automotiveforums.com/vbulletin/showthread.php?t=772041&page=1
.
.
When Fail-Safe Mode has been activated, next time powering up will cause P-Mode lamp to blink 8 seconds.
.
.
.
- SHIFT LOCK

EU Maxima models do not contain Shift Lock mechanism. Theres no shift lock solenoid at selector lever (handle), neither there is no control module under passenger side panel. Also ignition key solenoid is 'missing'. The user is free to use Shift Lever as he sees fit. The only device keeping 'TCU happy', is a 100ohm resistor substituting for the ctrl electronics (possibly just to pass the self diagnostics), see below. For Shift Lock details, see FSM AT-164.

.
.
.
- LINE PRESSURE DROP RESISTOR , see FSM AT-82

 

Overview:

Using the Line Pressure Drop Resistor, TCU regulates the oil pressure that the pressure oil pump generates. Resistor is located 'below air filter': Take the connector out, measure: 11.2 - 12.8 Ohms says the FSM page AT-58. Check other resistances according the A/T connector table below or see FSM. Connector is in the same harness as MAF connector, attached onto surge tank (blk 'bottle) near MAF, see below.
(Note that cheap multimeter's are not accurate near zero resistance measurements)
.
.
.
Modification to boost kickdown , enhance too soft gear change properties:

Short test after increasing the resistance to 90 Ohms -or- decreasing to 2 Ohms - had no effect on my current softness on gear 1--->2 change (lately returned). Disconnecting the drop resistor connector altogether, results in jerky sharp change (softness all but vanished) - feels like it will damage the tranny. Around 40mph, when second gear 'hits', both wheels 'burn' asphalt, no good for tranny ... After testing with multiple size resistors, I settled to 5kOhm. (At the moment this new setup seems healthy - I'll inform if/when the box blows)

In the end, I used the depicted WOT bypass switch (see below), installed at throttle body. The original Line Pressure Drop down Resistor stays intact - the 5kΩ works in series with the original resistor. It is used only when when gas pedal is fully pressed and the bypass switch opens. At Wide Open Throttle, WOT, the total resistance that TCU 'sees', is briefly the 5012Ω. This resistance increase results in firm but not jerky gear change. See the bypass schema below.

Current test settings, added features seen inside redline -box: yellow drop resistor wire is cut, new 5kΩ resistor added. Original resistor is never bypassed - at WOT the new 5kOhm resistor is added in series. (The connector is located near main brake cylinder). Picture at right: the WOT switch at throttle mechanism.

The Original Resistor below air filter box, rotten look...

Normally functioning tranny doesnt benefit from the add on feature. It only helps in case gear change from 1st -to- 2nd is too soft, and kickdown -problems. The underlaying problem might be internal leaking ... possibly the 15 year old o-rings...
.
.
Here's a video how it now goes from 1st to 2nd...
Clic Tranny 5k Resistor Mod
.
.
.

_____________________________________________________________________

 

.
.

2c.  Revolution Sensor, Solenoid, Inhibit Switch Connectors

.
.
.
Measuring TCU electronics Connector pins, solenoids:
.
The voltages I measured are about the same as the FSM list indicates, maximum voltage readings were about one volt less than battery voltage at that point.
.
.
The pin21 which should be the TPS "kickdown" switch:
I have found contradicting, at least three kinds of wiring diagrams on this Throttle Position Sensor switch.
Nissan FSM tells that this is "not used"... measurements at TPS tell the switch itself is functional.
Possibly different TCU versions use this TPS sw for shiftdown, but some other models calculate the speed how fast accelerator pedal is pressed, which is the case in my car as my tranny functions perfectly.
.
.
Transmission solenoid connector has to be cleaned to ensure they really get the voltage they need for proper function. The coil resistance can be also checked with multimeter from the connectors.

 

S1: Revolution sensor connector. S2: Solenoid connectors, S3: A/T Inhibitor = gear selector connectors.

Revolution sensor at left [3pins], the Solenoid connector at right [7pins]. (Solenoid pack is inside the tranny)

Correction to the picture: The Line Pressure Solenoid resistance is 12Ohms.
.
.
.

_____________________________________________________________________

 

.
.
.

2d. INHIBITOR SWITCH - later called |IS|

.
.
.

Overview:

|IS| is actually a sealed switch pack located on tranny, where stick control wire ends. Outside the |IS| is a switch actuating cam. Its 'fork' end follows the transmission gear selector arm pin. ( The transmission gear selector in turn is controlled by the wire and gear selector handle in the cabin.) The |IS| cam movement activates the related switches inside |IS|. On one side of the |IS| -box comes out the harness going to TCU.

Testing; connector pin definitions:

To measure |IS|, see for |IS| (S3) pins in this list; refer to FSM AT-81

 

|IS| looks physically like this. On top is seen the cam which follows tranny lever mechanism.

 

B, the |IS| follower cam alignment hole has to be aligned with A, the |IS| cover 'adjustment hole'. Arrows point to |IS| attachment holes which allow leeway in positioning.

 

.
.
Self Diagnostics Note: Prerequisite for successful Self Diagnostics, is a functional
- Inhibitor Switch |IS|,
- TPS zero -position Switch (see p.6) and
- Transmission Power/Comfort -Mode Switch.
(If Engine starts only in P and D -positions, |IS| is probably ok.)
.
.

|IS| Mechanics:

Electrical, selector position -related feedback to TCU comes via |IS| as TCU has to work in concert with mechanics/hydraulics. In the pics below, the gear lever ctrl wire [grn] is coming from the cabin, attached to A/T tranny mechanics. It is connected to a rod/cam [blue] with mechanism going in through the tranny box wall. See FSM page AT-195.
.
.

In the following pics, tranny cover & valve assembly has been taken out for illustrative purposes:

Inside the tranny, the [blu] selector/rod mechanism has a tooth edged sector. On this sector, there is resting a locking tooth [yellow] - spring forced. This locker mechanism positions the gear lever mechanically. You feel these notches ratcheting against the locker tooth when you push the gear selector in the cabin. The |IS| is not seen here, it is attached to the tranny side.
.
.
.
Selector - linkage: The A/T control steel wire from cabin is seen near the firewall, here green -false color. |IS| is located here (not in view from this angle).


Reverse clutch band, above, at left, is tightened with the cyan screw. When cover is at place, it may be possible (possibly!?) check it and tighten the band via the [cyan] hole in the tranny rear wall. Brake band servo piston rod [amber] seen at left. Check for the adj procedure at FSM page AT-236.
.
.
.
.
The Inhibitor Switch |IS| alignment; steps 1. thru 7.:

Inhibitor Switch Adjustment; Refer to FSM page AT-182
.
.
.

1. Disconnect the control wire [grn] from the transmission lever [blu] (=take out the [red] lock pin).
2. Loosen the three 8mm |IS| attachment screws.
3. Position transmission lever [blu] to N.

4. Align |IS| cover hole A --with-- lever hole B --with-- tranny lever C.
--->A-B-C .... In the end, all have to be in direct line - until check pin can be inserted. Insert an alignment pin (5mm, 3/16") short drill bit?.

5. Tighten the |IS| attachment screws.
6. Check that gear selector handle in the cabin is at N -position.
7. Adjust the control wire [grn] until it can be easily reattached into the tranny lever [blu].

Dont forget to lube wire and all bearing/sliding mechanisms.
.
.
'Peek view' between tranny and firewall: |IS|, Cam in orange color; Transmission mechanism is at N.

.
.
|IS| cam is now aligned with tranny gear lever [blu] for alignment. Transmission is at N

.
.
Click to enlarge this Zoom-in picture; ready for pin insertion (arrow):
A. - The |IS| cover align 'hole'
B. - the |IS| CAM align hole
C. - Tranny lever align hole

.
.
.

_____________________________________________________________________

 

 

.
.

2e. POWER - A/T - COMFORT -mode switch

.
.
.

Overview:

This switch 'assembly' contains two totally separate entities:

The Switch:

The Power-A/T-Comfort Mode Switch; informs TCU at what rpm level the gear changes are to be executed. The switch is connected directly to the TCU.  Based on this switch position, TCU varies its control 'pattern' on Line Pressure Solenoid valve inside the transmission. 

The Indictor Lamps:

On the Right side of the switch assembly, there are integrated Mode-indicator lamps, directly controlled from TCU. The lamps like the switch are NOT directly connected to each other but to the TCU. Based on the sw input, TCU varies its control mode and lightens those lamps.

When Lamps correlate to switch position, it means that TCU is functional up to a point. Except during diagnostics, the lamps do follow the switch position.

Switch Assembly as Self Diagnostics tool:

Prerequisite for successful TCU Self Diagnostics, is this functional Mode Switch. The Lamps are needed in code reading. The diagnostics procedure refers the top P -lamp as the Power Lamp.
.

Double Function Structure:
.
The 3-position Transmission Mode Switch. Power Indicator lamp P on top/right. These two Mode -indicator lamps P & C are used also for Self Diagnostics.

The Transmission Mode Switch, seen from rear, here lamps are out. The separate lamp wirings are indicated by yellow arrows. They have no connection with the Switch pins 1-5.

 

Switch Pins 1-5:
- In Power Mode (P-pressed down), only pins 1-2 are closed.
- In A/T mode, no connections.
- In Comfort -mode, only pins 2-4 are closed. 

If switch is broken , use bypass jumper wires between these pins to simulate the switch during self diagnostics, later open/repair it or get another.
.
.

_____________________________________________________________________

.
Switch Operation, user modes:

POWER             'Sporty' drive -style, P-light is illuminated, gear change rpm is high.

 A/T                        Identical to Comfort    -mode ... except when gas pedal is pressed suddenly
                                    (Then momentarily changes to Power-Mode, P-light is illuminated)

COMFORT        'Leisure' drive-style, C-light is illuminated, gear change rpm is low.

.
.
.

_____________________________________________________________________

 

.

Note: For troubleshooting the TCU main connector may be disconnected. Transmission will 'work' purely hydraulically, forward and reverse gears will at least engage...
.
.
------------------------------------------------------------------------------------------------------------------------------------------
A/T Self diagnostics click p.21 See also Service Manual Page AT-45.
------------------------------------------------------------------------------------------------------------------------------------------
To see A/T function principals, click http://www.howstuffworks.com/automatic-transmission5.htm
------------------------------------------------------------------------------------------------------------------------------------------

 

.
.
Knowledge is NOT Wisdom
  
...from knowledge >to> wisdom >to> ....
"Wisdom is the principal thing; therefore get wisdom: and with all thy getting get understanding";

Solomon
  
.
.

________________________________________________________________________________________________________________________

Click To Page: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 INDEX