Mike Beglitsoff, owner of the Automatic Transmission Center in San Francisco, took in a 2003 BMW 325i with a ZF5HP19 transmission stuck in 4th gear only failsafe. The double digit OE codes pulled were:
33 – Input/Turbine Speed Sensor (ISS/TSS) “A “Circuit Range/Performance
49 – Gear Monitoring
55 – Gear Ratio Error in 5th
65 – Gear Monitoring 4 at Electrical Substitute Program – ISS/OSS Ratio
Typically, whenever I deal with code 33 on ATSG's technical support line, it is a code that comes up after a rebuild. It wasn't the customer's originally complaint to be resolved. In these situations, the cause is usually due to the use of incorrect parts. To explain this requires a short history lesson with the ZF5HP19 transmission.
This unit was used in Audi vehicles as early as 1996. At that time, the ISS/TSS was a pulse generator type mounted on the top side of the valve body. This sensor was excited by sheet metal windows integrated into the spider clutch bell. Around 1998 a change was made to use an ISS/TSS Hall Effect type sensor. The sensor location was changed from being on the top side of the valve body to being mounted on the case. This was done so it could be excited by a magnetic band of 36 magnets now placed around the “A” clutch drum. Since the A clutch drum sat inside the sun-shell, for the ISS/TSS hall effect sensor to read the magnets on the A clutch drum, the material of the sun-shell was changed from metal (a ferrous material) to a non-ferrous type shell.
This change affected only some models in 1998 and was implemented over time to as late as 2002 in all the other Audi vehicles equipped with the ZF5HP19 transmission. Volkswagen Passats’ from 1999 to 2001 was also part of this change.
As a result of this switchover, there now becomes two different “A” clutch housings, two different spider clutch bells and two different sun-shells. These parts are not interchangeable in any way. A mismatch of these parts will render the ISS/TSS ineffective; in other words, no signal. The same problem can occur by simply installing an incorrect exchanged transmission. The pass through connectors for either type sensor has the same configuration allowing for such an error to occur.
Getting back to BMW, they began using the ZF5HP19 transmission in 2000. Vehicles using this transmission only received the Hall Effect type arrangement. Should a pulse generator type sun-shell and/or “A” clutch drum be used, code 33 would immediately pop up after a rebuild. Once code 33 is set, all other ratio errors/gear monitoring codes should be secondary in the diagnostic process as they may be a byproduct of code 33.
But this was not the case with Mike’s 2003 325i. It arrived with these codes and it was not previously worked on. An initial check of the ISS/TSS was performed and it had a clean 5 volt pulse all the way to the TCM. He then ran checks on all the circuits and each check passed. The ONLY discrepancy was the battery voltage PID he saw in his scan tool with what he was seeing with his meter. The scan tool PID showed erratic voltage. Especially when driving. It would go from 14.5 down to 12.5. But an actual volt meter checking battery voltage at the TCM it remained steady at 14.7.
One of Mike’s employees named Andy owns and drives a 2000 323i which uses the same type transmission. Looking at his vehicle with a scan tool revealed a steady battery voltage PID. It took some pleading but he convinced Andy to let him try the 2003 TCM in his vehicle. When he did, he noticed the battery voltage PID in his scan tool remained erratic as it was in the 2003 325i. Yet the volt meter monitoring TCM battery remained steady. In fact at one point the scan tool PID jumped up well past 15 volts while the volt meter remained steady. With that, it was finally decided to obtain a new TCM which indeed fixed the problem. It was this erratic battery voltage PID compared to the actual power supply that offered up a possible reason for all the ratio/gear monitoring related codes the 325i was experiencing. A good tip to remember should one roll into your shop like this.
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