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4L60E doesn't shift automatically when hot

 
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JFD444 JFD444
New User | Posts: 2 | Joined: 12/11
Posted: 12/02/11
10:13 AM

I have a 1994 Chevy C1500 4.3L with a 4L60E transmission.  I use it as a postal carrier and after about 45-60 minutes of stop & go driving it will not shift up or down automatically. Occasionally it will start to work for a few minutes and then stop again. I can shift it manually into 2nd,D and OD but it will not engage 1st gear.  It doesn't feel like it is slipping before it stops shifting and after I shut it off for about 20 minutes it starts working again. The fluid & filter have also been changed on a regular basis.  Any ideas what may be causing this?  

440t4 440t4
Guru | Posts: 1009 | Joined: 04/09
Posted: 12/02/11
10:28 AM

The computer is locking the trans in limp mode. You need to scan the computer and get the codes. Post them here and we can help you.  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 12/02/11
10:44 AM

94 and 95 is a problem year.. for diagnosis.. as you cannot pull codes without a scan tool..  and that is an OBD1.5 system..

one of these are the diagnostic connector under the dash board..

42140733

if you get a scan tool check for codes... write them down..

here is a list of the live data that can be examined and compared to the scan tool readings.. please ONLY read one line at a time..

Scandata



you could just change some of the electrical components.

the manual lever position sensor..

the solenoid pack...

along with the filter and fluid..

checking the codes is the first place to start...  as when it quits shifting.. it WILL set a code.. but may NOT turn on the check engine light..  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 12/02/11
10:51 AM

it will take a full fledged scan tool to check the codes on that model..


something like an OTC monitor 4000 version..  monitor extended..  extended monitor..

Otcmonitor4000e

an OTC genisys

Otcgenisys

a snap on MT2500

Mt2500snapon



a monitor 2000 WILL NOT WORK ... its only good up to 89 model years..

OTC2000
this picture is a monitor 2000.. it will not work on GM  newer than a 1989..

these scan tools can be sometimes purchased on craigs  list.. for usually around 200 to 300 bucks.. sometimes less.. be sure it has the cartridge.. and the proper cable.. for your application..  

440t4 440t4
Guru | Posts: 1009 | Joined: 04/09
Posted: 12/02/11
11:18 AM

There are two pins you can jump together and the computer will flash the codes out on the check engine light but i dont remember which two. I think it was pin 2 and 4 on the 16 pin connector.  

JFD444 JFD444
New User | Posts: 2 | Joined: 12/11
Posted: 12/02/11
02:08 PM

OK, I pulled the following codes by using a jumper & recording the flashes.

35-Idle Air Control
43-Electronic Spark Control / Replaced Knock Sensor but code still re-appears
59- Transmission fluid temperature sensor-low temp (below -40 ***

Where should I start?  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 12/02/11
03:16 PM

59 is what's kicking you ...


here is some info on code 35

http://www.autozone.com:80/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80c90f7c

testing the knock sensor...  part of the spark control.. but not all of it...

http://www.autozone.com:80/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80c90f66

i don't have transmission info on 59 right this second.. i will return with more..

it could be a bad wire .. loose connector.. bad harness inside the transmission.. bad temp switch inside the transmission..   loose ground wire between the engine and body.. or engine and battery..

more to come..


T74425NC

Solenoid, TCC & Wire Harness, (Replaces All 93-96-2002 OE Harness)
Will even fit early 1993 models if updated by ordering # 74442 Manifold Pressure Switch
Common brands - Rostra


74445GK

Repair kit, 4L60E external wiring harness (13 pin connector) 1993-UP
Part #: 74445GK


i cannot seem to find a picture of the transmission temp sensor.. by its self.. perhaps its embedded in the harness.  

440t4 440t4
Guru | Posts: 1009 | Joined: 04/09
Posted: 12/02/11
04:00 PM

The code 59 is most likely a bad TFT {transmission fluid temperature} sensor. The second most likely cause is a bad transmission internal wire harness. The third most likely is the harness between the computer and the trans and/or the computer itself. The TFT sensor is part of the valve body manifold pressure sensor which is right under the pan and is easy to change. To replace the internal wire harness you have to drop the valve body.  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 12/02/11
06:02 PM

TFT is the Transmission Fluid Temp sensor

i don't know which of the codes is the earlier 59..
~~~~~~~~~~~~~~~~~~~~~~~
P0710 - GM
Type Powertrain - Transmission - ISO/SAE Controlled
Description
TFT Sensor Circuit Low Input Conditions
Cause
No TFT sensor codes set, engine running, then the PCM detected a low TFT input based ECT and IAT inputs for 25 6 seconds
~~~~~~~~~~~~~~~~~~~~~
P0711 - GM
Type Powertrain - Transmission - ISO/SAE Controlled
Description
TFT Sensor Range Performance Conditions
Cause
Engine running, ECT sensor input less than 80°F after exceeding 160°F, ECT and IAT sensor inputs within 10°F of each other, then the PCM detected that the TFT sensor input was within 10°F of the IAT sensor input during startup, condition met on 2 ignition cycles

~~~~~~~~~~~~

P0712 - GM
Type Powertrain - Transmission - ISO/SAE Controlled
Description
TFT Sensor Circuit Low Input Conditions
Cause
DTC P0560 not set, key on or engine running, then the PCM detected a TFT sensor input of 298°F or more (200 mv or less) for 5-10 continuous seconds

~~~~~~~~~~~~
0713 - GM
Type Powertrain - Transmission - ISO/SAE Controlled
Description
TFT Sensor Circuit High Input Conditions
Cause
Engine runtime over 3 minutes and 20 seconds, ECT sensor input over 1°F, then the PCM detected that the TFT sensor input was more than -35°F, condition met for 30 seconds Refer to the correct code repair chart in other manuals

~~~~~~~~~~~~~~~~

P0714 - GM
Type Powertrain - Transmission - ISO/SAE Controlled
Description
TFT Sensor Circuit Intermittent Conditions
Cause
Key on or engine running, then the PCM detected that the TFT sensor input changed 0.2v or more (a 10°F change), condition met for less than 1 second Refer to the correct code repair chart in other manuals


there is a specific chart for code 59.. but my engine drivability manuals don't cover the transmission codes..  

440t4 440t4
Guru | Posts: 1009 | Joined: 04/09
Posted: 12/02/11
06:37 PM

59 says the computer is reading high voltage. Which i believe correlates to low temperature. If it was in my shop i would try another manifold sensor before i started looking into the external harness i always have a few good ones around. And when the pan is down you can check continuity on the TFT internal wires pretty quickly.  

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