- Author: Certified Transmission
Case number 2009-1
A 1997 Audi A4 Quattro 1.8L turbo (ZF 5HP19) with a complaint that the transmission lost reverse once it was warmed up.
This transmission has a history of chronic reverse problems. The vehicle was scanned with a MODIS and presented the following codes: 00652, 18010 and P1602.
The multiple definitions of the code 00652 include references to a ratio error, gear monitoring and transmission range sensor. Both of the other codes refer to power supply being too low. The battery tested good after a recharge, and since the vehicle had been sitting it was no surprise that it wasn’t fully charged when it arrived at the shop. The road test confirmed no reverse. Even after unplugging the transmission solenoids there was still no reverse. The shop recommended replacement with a remanufactured transmission. All indications were that this was the correct and proper diagnosis and recommendation.
This particular unit was the subject of a tech bulletin recommending an updated reverse drum and snap ring, which are included in the Certified reman unit.
After the shop installed the remanufactured unit, the transmission exhibited the same condition: no reverse once warmed up.
At this point, the shop contacted the Certified Transmission Warranty Tech Support Team. Additional research revealed that code 00652 also refers to a problem with the MLPS. We recommended that the shop replace the MLPS and perform the module initiation process “ISO.” The shop did so only to find that the unit still had no reverse once warmed up.
The unit was returned to Certified for warranty rework. Finding no internal problems, Certified installed a new valve body and returned the unit to the shop for installation. To everyone’s dismay, after installation of the unit, the “no reverse once hot” condition was still present. The “ISO” procedure was repeated with the MODIS as well as numerous tests on the solenoids to rule out the M3 solenoid, which inhibits reverse under certain conditions. A lot of time was spent trying to test them via wire diagrams and voltage checks.
After a “call for help” was sent out via Internet forums, a suggestion was made to use a VAG-COM to perform the “ISO” procedure. The shop eventually got their hands on a VAG-COM and ran the “ISO” procedure one more time. This time it worked to perfection!
The lesson: A lot of time was spent studying wire diagrams and running voltage checks, added expense for shipping, warranty repairs, replacing the valve body and additional R&R time. The job could have been completed quickly with the right tools in the first place. On today’s complex computerized vehicles, you simply cannot compromise on test equipment. This isn’t a commercial for the VAG-COM, but in this case it appears that the MODIS (as great a tool as it is) simply didn’t work correctly.
This car stayed in the shop for four full weeks. There is no way of knowing whether replacing the MLPS and using the VAG-COM to perform the “ISO” procedure would have taken care of the original problem, but in the absence of information to the contrary, and because updates were specified for this unit, we can only assume the problem was at least partially due to internal issues. It’s like the old dilemma of which came first, the chicken or the egg.
Certified Transmission remanufactures several hundred transmissions every week. Computers, electronics and general drivability issues are often the root cause of the problem that a shop is trying to resolve with a replacement transmission.
Recognizing that many post-installation concerns are due to inaccurate diagnosis or improper installation, Certified has partnered with Transmission Digest to produce articles examining these types of situations through the real-life inquiries received by the highly skilled technicians who support Certified’s “no-fault” warranty program.