ZF 6HP26: A torque calculation error - Transmission Digest

ZF 6HP26: A torque calculation error

A 2008 Lincoln Navigator with a ZF 6HP26 transmission arrives at Holcomb’s Transmissions in limp. When checked for codes, a P1719 comes up for “Inaccurate Engine Torque Signal.” The TCM receives this over the CAN, causing it to initiate failsafe.

The information Ford provides for this code is vague. The Action step provided is to simply monitor the appropriate PID to validate that an error is present. The PID chart provided for this step consists of transmission-related information followed by instructions to clear all DTCs, and once cleared, test the system for normal operation. If the DTC returns, the tech is to refer to Computers and Control Systems.

This leaves many scratching their heads, not sure what they are meant to be looking for. In this case, the tech did clear P1719 which allowed the transmission to begin shifting again—but for just as few drive cycles before the code set and the transmission went into failsafe mode.

With engine torque reduction being used for many years now for a variety of reasons, when there is a problem with this computer strategy, one of the first things to look for is what other codes may be lurking in the system. Additionally, you should look at sensors related to engine load such as air filters, MAF sensors, throttle bodies, TPS, APPS, etc. Sometimes a new air filter, cleaning of the MAF and/or throttle body resolves the issue.

In this case, the tech working on the vehicle only pulled P1719. ATSG tech Al Sanchez suggested scanning for OBDII generic to see what codes might be found there. When he did, two codes came up that offered a clue to the problem: Code P0171 for fuel system too lean (Bank 1), and P0174 for fuel system too lean (Bank 2). Al immediately asked the tech to examine that air intake system to see if there was a vacuum leak allowing excessive air to be sucked into the system. In doing so, the tech discovered a vacuum leak at the throttle body where the bellows hose was not fully seated. After coupling it back into place (see the image above), codes erased, and a road test confirmed that the problem was resolved. It was quick calculating of a torque calculation error once the lean codes became exposed.

Read more stories from our Technically Speaking column series here.

You May Also Like

Shift of the shaft: Diagnosing Chrysler 48RE manual shaft issues

The TorqueFlite transmission has been around since mid-to-late 1950s. There have been many changes surrounding the manual shaft and rooster comb through the years. This transmission shaft controls the position of the manual valve that directs oil for the gear ranges, but it also is used for a Reverse light control as well as Park/Neutral

The TorqueFlite transmission has been around since mid-to-late 1950s. There have been many changes surrounding the manual shaft and rooster comb through the years. This transmission shaft controls the position of the manual valve that directs oil for the gear ranges, but it also is used for a Reverse light control as well as Park/Neutral safety control. As it evolved, changes to these safety backup switches caused extra stress against the rooster comb that posed new challenges to the technician. 

Sometimes, a diagnostic code is all you need

With ATSG having the opportunity to help shops solve problems, sometimes we get faced with some real doozies. A shop will call and give us a laundry list of DTCs, leaving us to think someone must have a bulkhead connector unplugged. We then go through the arduous task of deciding which codes prompted other codes

10L80 and 10R80 pump gear differences

You may have seen an article in the August 2023 issue of Transmission Digest called “GM 10L80: A new kind of pump noise,” which goes over how the front cover housing in the 10L80 is fitted with a converter drive gear and idler gear. The idler gear drives the pump’s driven gear, and is press

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

Going the extra mile: Proving your transmission repair suspicions

A 2003 Honda Pilot with a five-speed three-shaft transmission came into our shop with a customer concern that the vehicle had no power, and the “D” light was flashing. I first did a scan for codes to see what it came up with, and the scan tool returned four DTCs: P1298 (ELD voltage high), P0135 (H02S

RRfeature-1400

Other Posts

Alto releases friction and steel module for ZF 6HP transmissions

Alto has introduced a new friction and steel module for ZF 6HP series transmissions. The module works with ZF 6HP19/X/A (model years 2004 and on) and ZF 6HP21/X (model years 2007 and on) for ZF, Audi, BMW and Volkswagen vehicles. Related Articles – Alto introduces filters for GM 6L series – PRT launches 30 new

ATSG shop management training seminar coming soon

ATSG announced that it will soon be holding a series of management training classes for shops, beginning at the end of January. Related Articles – Are you down with CVT? – Shop Boss adds new user interface to its shop management software – How seriously should shops take the EV wave? Jonathan Sherman’s Management Training

ATSG-Sherman-1400
Spotting different 68RFE designs through the years to avoid issues

The Chrysler 68RFE has had several changes through the years. Its four-speed predecessor began with a noisy solenoid pack identified by a black colored pass-through case connector (seen in Figure 1).  Related Articles – Valve body and component suppliers: A comprehensive list – Shift Pointers: Failures caused by incorrect tire sizes – Understanding lube flow

Valve body and component suppliers: A comprehensive list

Looking for a comprehensive list of the industry’s valve body and valve body component suppliers for 2024? TD has you covered. Below, find a list of suppliers including contact information, addresses, etc. Related Articles – How reading through service bulletins can turn a technician into the customer’s hero – Sometimes, you should sweat the small