Stuck On, Stuck Off or Just Plain Stuck - Transmission Digest

Stuck On, Stuck Off or Just Plain Stuck

With the introduction of OBD-II, a ton of additional codes became available (remember, we were always asking for more information). In some instances, these new codes were a great help because they did not just indicate a short or an open circuit but also pointed to parameters that were out of range, which included both mechanical and electrical problems.

Stuck On, Stuck Off or Just Plain Stuck

Shift Pointers

Author: Pete Luban

Shift Pointers

  • Author: Pete Luban

With the introduction of OBD-II, a ton of additional codes became available (remember, we were always asking for more information). In some instances, these new codes were a great help because they did not just indicate a short or an open circuit but also pointed to parameters that were out of range, which included both mechanical and electrical problems.

And then sometimes, they were no help at all, just confusing and, in some instances, totally misleading!

Here’s the problem: OBD-II codes can be either generic (usually displayed as a “P0” code) or manufacturer specific (usually displayed as a “P1” code).

That being said, this article pertains to torque-converter-clutch (TCC) codes that are in the P0700 generic group; for example, P0740, P0742 and P0743. OBD-II generic codes supposedly are required to mean the same thing no matter which company made the vehicle.

However, it doesn’t mean that it has to be the exact same code, only that it must refer to the same general symptom. For example, the code for a mechanical TCC slip is P0742 for a GM vehicle, but it’s P0770 for a Lexus. Whether this complies with the OBD-II mandate doesn’t matter; this is just the way it is. Heck, some of the European auto manufacturers don’t even make these codes available, or they made them available for a model year or two and then they were gone.

When you look at the charts in figures 1-5, you will notice that code P0740 for a 1996 GM car equipped with a 4T60-E is mechanically generated, nut the same code for a 1997-98 GM truck is electrically generated. (This is within the same auto manufacturer!) Meanwhile, a 1997-98 Toyota uses P0770 for the mechanical fault and P0773 for the electrical fault, and a 1997-98 Nissan uses P0744 for the mechanical fault.

Also notice in figures 1-5 that some OBD-II codes were available in the 1994 model year. There were vehicles with OBD-II in the 1994 and 1995 model years because the manufacturer was “road-testing” the new diagnostic system to make certain it would function properly when OBD II became mandatory beginning with the 1996 model year.

As you can see, this becomes very confusing for a technician trying to interpret one of these codes properly – especially when Toyota, for example, defines code P0770 only as “Lock Up Solenoid.” Not very helpful, is it? Of course, what happens most of the time is that the lockup solenoid is replaced and the problem still exists.

When a mechanically generated code is stored, regardless of the code definition, it usually means that the computer has seen an incorrect engine- or vehicle-speed signal when TCC is commanded on or off.

In other words, a “Stuck Off” code results in TCC being commanded On, but the computer sees either TCC slip or too-high engine speed.

A “Stuck On” code means just the opposite: TCC is commanded Off, but the computer sees too-low engine speed. These scenarios are mechanically generated, not electrical!

Then there’s a bunch of codes for the TCC-solenoid electrical circuit that are also in the P0700 group. Also, there’s a rather large number of other electrical codes for the TCC solenoid, but they are manufacturer-specific, or “P1,” codes, which is another story.

I hope the charts contained in this article will help save some time and unnecessary parts costs. As for me, I’m gonna take a vacation after this one!

P.S.: Always use the generic part of your scan tool on the European vehicles; you never know – you might get lucky!

Pete Luban is a technical consultant for the Automatic Transmission Service Group (ATSG) and a frequent contributor to Transmission Digest.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

Shift Pointers: Where’s that fluid leak coming from?

A 2016 Honda CRV 2.4L (Figure 1), using a BLJA CVT 4WD transmission (Figure 2) comes in to a shop with a customer complaint of a leak. Related Articles – The torque converter can of worms: Lockup and aftermarket programming – The Subaru mystery burn – Multitasking: Sorting out multiple issues with the same vehicle

Ford 8F35 maintenance tips: Planetary failure and no-pressure conditions

Our shop has had several vehicles come in with the Ford 8F35 transmission having planetary failure. Apparently, there was a run where the pinion needle bearings had a hardness problem (see Figure 1). Related Articles – Chrysler RH/RE late shifts and high pressure – Ford 6R80 shift solenoid ‘E’ resistance change: How to tell the difference

Figure 12.
Shift Pointers: A Chrysler 300 no-shift complaint

The case study has to do with a 2009 Chrysler 300 C 5.7L Nag1 RWD with 71,923 miles on it (see Figure 1, above). Related Articles – How to get around non-serviceable GM 6T70/75 self-tapping pump screws – Shop Profile: AAction Transmissions begins a new era by trying to reach a new generation of customers

Shift Pointers: What to do when the 62TE TRS tab breaks

How frustrating it is when on a hot summer day, as you go to open a nice cold can of your drink of choice, and the tab breaks off? You are outside, away from any tools to remedy the problem quickly. It now requires a MacGyver mentality looking around at the resources available to get