No 3rd or 4th gear - MAXIMA 00

[lockeed]

Even when the car is stopped, I get clear and long reading of 4.5V from the vehicule speed sensor terminal (#40) ? Why does it stay there?

Also for the alternator, I see that the regulator in built in the alternator on mine (it looks like it, haven't checked the specs). Would it be good to check the ground (or add one) before replacing it?

One last one, when a regulator get toasted, does the voltage always go up at the battery terminals ?

Because when I start the car, my V. reading seam to get lower...

[Nahkapohjola]

Originally Posted by lockeed

Even when the car is stopped, I get clear and long reading of 4.5V from the vehicule speed sensor terminal (#40) ? Why does it stay there?

Also for the alternator, I see that the regulator in built in the alternator on mine (it looks like it, haven't checked the specs). Would it be good to check the ground (or add one) before replacing it?

One last one, when a regulator get toasted, does the voltage always go up at the battery terminals ?

Because when I start the car, my V. reading seam to get lower...

- For the sensor, the TCU is the supply-source 'route' for power. The 'sensor' chops this voltage signal each time magnet passes it and gives the chopped signal as the output. Thus rotation causes square wave output; the wave amplitude - or 'square length' related with speed. No movement = no chopping... Depends on sensor type and/or magnet position what the output happens to be while stationary.

- add jumper wire from alternator into chassis = test grounding. However, I suspect your alt has already passed.

ALTERNATOR
- yes your alternator contains the rectifier and voltage regulator. But you can buy them separately. If you like tinkering, DIY. Swap new bearings also...
- brushes wear out 'at 100k miles' = warning lamp comes on flickering or full, meaning no charge.
- Theres the writeup linky below how to change the brushes (older 3gen model, but no big diff with 4gen maxima) ... and/or the regulator.
- Go buy smtg new: Brushes few dollars, regulator 50$, replacement 'factory repaired' alt 200$, new 2000$.... approx.
- You have to open it to see if brushes are worn. You may buy just the brushes, or the regulator assy with brushes - and swap. Remember the dust cleanup which may be shorting tha alt rectifier diodes. Stupid copper-dust 'feature' like most cheap issues in our vehicles. This issue may hamper 'any' vehicle driven over 60k.
- Most people buy another alt. I changed brushes because $$$ and I wanted to keep the original alternator - as the factory repaired tend to last one year - possibly problem with oxidation due to ? harsh cleaning fluids for the used alu shrouds at repair-factory... read the writeup and how to go around that problem.

When engine is started, it always consumes power to keep it running. All kinds of peripherals suck power along with ignition, computers... If no charge, then power is taken from battery. This means batt voltage surely drops, engine will die ... in an hour?
Low voltage: The tranny computer TCU seems to be the first to become asthmatic ... far earlier than the engine ECM: possibly logic ? uses IC's with 12v supply features.

[lockeed]

I cleaned all ground terminals in the engine bay today. I also cleaned the alternator + post and properly re-did my battery post connections so they are tight and firm.

Battery read 12.6V, after starting the car, reads 13.5 / 13.6V... good sign... (lets hope it last...)

I also did some tests again with the TCM. I went on the road and monitored the Shift solenoid A and B terminals with a multimeter. As expected, they come On and OFF depending on the gear you select. They seam to work fine. I tested the TPS and switch again, all is within specs. This kind of point out to either a mechanical tranny problem, or the TCM that might still be fried or unprogrammed....

Again, what makes me believe that there's a "software" issue with the car is that the transmission drop back from 2nd to first gear whitout notice or being needed... Also, let's say I'm doing 75km/h and I punch the gaz, it'll try to engage 1rst gear even if the car is traveling way too fast... that makes me believe that the TCM has an improper "speed" refference somehow... I already swapped the rev sensor, I tested it also with a multimetter so I know it's alive. My abs and speedo works properly... I just don't know where to look now... There should be a "vehicule speed sensor" on the trasmission, just not 100% sure where to look...SOme say on top of the differential... I tested it's terminal on the TCM while on the road but it gave me all sorts of voltages... Don't know if they're good or not...

Can the ECM be unprogramed or fried and sending wrong data to the TCM ?

Is it possible to flash (reprogram) a TCM ??

[Nahkapohjola]

Originally Posted by lockeed

I cleaned all ground terminals in the engine bay today. I also cleaned the alternator + post and properly re-did my battery post connections so they are tight and firm.

Battery read 12.6V, after starting the car, reads 13.5 / 13.6V... good sign... (lets hope it last...)

I also did some tests again with the TCM. I went on the road and monitored the Shift solenoid A and B terminals with a multimeter. As expected, they come On and OFF depending on the gear you select. They seam to work fine. I tested the TPS and switch again, all is within specs. This kind of point out to either a mechanical tranny problem, or the TCM that might still be fried or unprogrammed....

Again, what makes me believe that there's a "software" issue with the car is that the transmission drop back from 2nd to first gear whitout notice or being needed... Also, let's say I'm doing 75km/h and I punch the gaz, it'll try to engage 1rst gear even if the car is traveling way too fast... that makes me believe that the TCM has an improper "speed" refference somehow... I already swapped the rev sensor, I tested it also with a multimetter so I know it's alive. My abs and speedo works properly... I just don't know where to look now... There should be a "vehicule speed sensor" on the trasmission, just not 100% sure where to look...SOme say on top of the differential... I tested it's terminal on the TCM while on the road but it gave me all sorts of voltages... Don't know if they're good or not...

Can the ECM be unprogramed or fried and sending wrong data to the TCM ?

Is it possible to flash (reprogram) a TCM ??

13.5V is not good AT BATTERY... It means TCU voltage too low. Work on it until you get 13.8V -or- the normal 14.2V. First things first: Low power means semi paralyzed logic.

Charge voltage - 14.2Volts at battery mean 13.5Volts at TCU, which is healthy. Anything less and youre wasting your time in this case... On 'normal non problematic vehicle' 13.8Volt can be accepted, if new alternator swap 'is to be scheduled'.



Everything is possible, however, no procedures exist. If you take eproms out, UV-erase, and have a eprom programmer, it can be done. But where would u get any better program...?

ECM & TCU work in tandem, surelly affect each other. How they do it, I dont know of any info given... Try to swap. But with low power, no point.

ECM has one basic datatable. Then it has second datatable used in 'learning'. FSM depicts the 20minute learning drive with various drive 'phases'. This ECM memory is cleared via taking batt off 30min or more... This feature basically re-tunes new swapped MAF signal handling with the rest inputs: all the low grade MAF units are individuals 'having their own lifestyle' and their output signals like blondies. However, ECM learns in 'four' hours of normal drive, cleaned=learning ECM gives more jerky drive.

Btw. If power is at loss, clean the MAF and clear ECM as depicted...

[lockeed]

Just want to specify that the 13.5V I got at the battery was with both + and - terminals connected as usual on it. To test the alternator output voltage, should I unplug the + terminal and test on it directly, whitout it being connected on the battery? (to make sure)

Also, the warning "battery" light in the dash went away.

Bit I agree, I would expect to see closer to 14V coming from a healty alternator....

[Nahkapohjola]

Originally Posted by lockeed

Just want to specify that the 13.5V I got at the battery was with both + and - terminals connected as usual on it. To test the alternator output voltage, should I unplug the + terminal and test on it directly, whitout it being connected on the battery? (to make sure)

Also, the warning "battery" light in the dash went away.

Bit I agree, I would expect to see closer to 14V coming from a healty alternator....

Batt pole tst is ok. However, there is a brewing problem. Before swapping alt, verify your reading with another multimeter, maybe the fault is there. Would not be the first time...

As depicted, the alt two connector pins itself can be loose. Check.

[lockeed]

A quick update.

I replaced the battery and now I get a very good voltage reading from the alt and bat. 14.7V +

When for a quick drive, car does the same thing.

One question: when the engine is warm, if I give it some throttle (anywhere from 10% up to 50% I'd say), the rpm will over around 1600-1700rpm as if it was in cutoff mode. Going up to 1700RPM then quickly back to 1600rpm while the ignition seams to momentarely cut, then back and forth over and over again...

What is that? I suspect the closed throttle position sensor but might be wrong... What do you guys think?

[Nahkapohjola]

Originally Posted by lockeed

A quick update.

I replaced the battery and now I get a very good voltage reading from the alt and bat. 14.7V +

When for a quick drive, car does the same thing.

One question: when the engine is warm, if I give it some throttle (anywhere from 10% up to 50% I'd say), the rpm will over around 1600-1700rpm as if it was in cutoff mode. Going up to 1700RPM then quickly back to 1600rpm while the ignition seams to momentarely cut, then back and forth over and over again...

What is that? I suspect the closed throttle position sensor but might be wrong... What do you guys think?

- you have to run diagnostics, maybe some sensor dead. That drops engine into 'safe-mode' with rpm limit?
- buy a 100$ diag tool displaying all CEL codes. Find one which may be always on, while displaying all valid current codes plus error codes.

- Throttle pos sensor TPS, engine uses only when warm ... (however, tranny 'needs it')

[lockeed]

The engine is not in safe mode I think. The rpm fluctuate when the engine is warm and I press the trottle when in park, anywere from 5% up to 50% aprox. On the road, I don't feel any hesitation.

If I press more than 50%, the RPM climb normaly up to redline. Also, If I quickly blip full trottle, it'll take it just fine. It's just that 5-50% part that makes the engine cutoff at 1700rpm somehow...

I already pulled the codes, I had one for the canister valve near the gaz tank (repaired), and -P0744 Torque Converter Clutch, Solenoid Circuit Intermittent

[Nahkapohjola]

Originally Posted by lockeed

The engine is not in safe mode I think. The rpm fluctuate when the engine is warm and I press the trottle when in park, anywere from 5% up to 50% aprox. On the road, I don't feel any hesitation.

If I press more than 50%, the RPM climb normaly up to redline. Also, If I quickly blip full trottle, it'll take it just fine. It's just that 5-50% part that makes the engine cutoff at 1700rpm somehow...

I already pulled the codes, I had one for the canister valve near the gaz tank (repaired), and -P0744 Torque Converter Clutch, Solenoid Circuit Intermittent

"I press the trottle when in park"
- only in park?
- cold = ok?

Full throttle blip bypasses O2 input. The 02 sensors on 99% of cars are cheap and cant follow full gas flow, thus computer uses a datatable and compares it to rpm signal when controlling injectors.

Warm: No TPS used in engine mgmt. Instead O2 feedback is the main input (+MAF & rpm) to determine how injectors are controlled.

Test: while in Park, pull MAF connector plug out. This will cause 2.2k rpm ceiling - but your 1700rpm hesitation will be gone if MAF is bad. Push the plug back in...

Possibly O2 signal(s) warped. Signal, computer problem... Or maybe exhaust pipe leaking = oxygen seeps in distorting O2 signal.

However, diagnostics should indicate when O2 signal is amiss. Run the diagnostics. Pull the rhe diag codes, could ? be different. Anyways, diagnostics use the 3rd O2 sensor - which is maybe only used in diagnostics only. Dunno, the jap FSM translation isnt too accurate. You know service manual blondies syndrome.

Whatever, first ensure full voltage at both computers, TCU, ECM.

[ktechoz]

I have exact problem with my gear box!!
I hope you had fixed your tranny problem.

My gear box goes 1-2-2-1, not 1-2-3-4 as it should be.
All other parts in the car are in excellent condition, I suspect solenoid A and/or its valve (in the tranny box) is not working!
I shall drop them and have a look around....

[01_pathfinder3500]

Have you been able to figure out the problem? I just bought an 01 Pathfinder with the same exact issue. It will shift from 1st to 2nd smoothly but won't shift to 3rd or OD. I tested with my OBDII scanner and get 2 crankshaft position codes. One code for the sensor itself and one for circuit A. Codes p1335 and p0335.

Would that cause transmission troubles like i explained?