- Author: Randall Peterson
- Subject Matter: Diagnosis
- Unit: 01M
- Vehicle Application: 1998 Volkswagen Jetta
- Issue: No fourth gear
A 1998 Volkswagen Jetta with a 2.0-liter engine and 01M transmission came in with a complaint of not shifting into fourth gear. The owner had just bought the car, which had the problem when he bought it, and he said it would shift normally up to third gear.
Needless to say, the history of repairs is minimal at best. What we do know is that the owner took the vehicle to a nearby transmission shop, which pulled trouble codes. DTCs for shift solenoids 6 & 4 (N93 & N91, respectively) were present, so they replaced solenoids 6 & 4 and the internal harness. The trouble codes returned immediately. That shop didn’t know what to do from there, so they referred the vehicle owner to our shop.
As I pulled the vehicle around to do the preliminary checks, I found that it was not taking off in first; in fact, it was taking off in third. The second thing I noticed is that the OE radio had been replaced with an aftermarket unit. Before I connected my scan tool I checked for voltage on the K-line. There was battery voltage on the K-line so I removed the radio, removed the K-line from the radio connector, and taped it and relocated it so it wouldn’t get reconnected. Now I connected my scan tool and found trouble codes for all the shift solenoids. I wrote them all down, cleared them and retested. DTCs for SSV 6 & 4 returned. This was my starting point.
First things first; I performed an electrical-system test to find the health of the battery and charging system. The alternator had markings from a salvage yard, so it was suspect. It tested OK but the battery was weak. My next step would be to look up the specific information on these codes, solenoid specifications and wire diagrams.
The TCM (J217 in Figure 1) is under the rear seat and is easily accessible. There is published information about wire-harness issues inside the vehicle, so I started my testing at the TCM. First I made sure the computer’s power and ground connections were correct. Battery voltage is supplied to pin 45 (marked T68a/45) at the TCM from the fuse/relay panel under the driver side of the dash.
When I back-probed pin 45, it measured B+ with the vehicle running through all the ranges. Pin 15 (marked T68a/15 in Figure 2) is the B+ signal from the brake switch to the TCM. It was functioning correctly.
Pin 1 at the TCM is the ground. With the engine running I back-probed pin 1, and the voltage drop on the ground- side was 0.02 volt through all the ranges.
The computer supplies the power to these solenoids (Figure 4) from pin 67 of the TCM to pin 1 at the transmission connector. There should be B+ present at all times with the ignition on. There was 5.4V when I tested it, so something was wrong here. I suspected a faulty TCM but needed to test further to make sure there were no other issues.
I disconnected the TCM and connected my digital multimeter to pin 67 of the TCM connector and performed a resistance test on all the solenoids. There are seven solenoids in this transmission. Solenoids 1 through 5 and 7 should read 55-65 ohms. Solenoid 6 is the EPC solenoid and should be 4.5-6.5 ohms.
Solenoids 1, 2, 3, 5 and 7 measured OK at 63 ohms. Solenoid 4 measured 4.7 ohms, definitely out of specification. Solenoid 6, EPC solenoid, measured OK at 5.6 ohms. Knowing that resistance testing is only a part of testing electrical circuits, with the TCM still disconnected I powered pin 67 with a fused jumper wire, put my amp probe around a wire connected to battery ground and grounded each solenoid, noting the amperage.
Solenoids 1, 2, 3, 5 and 7 measured 0.174 amp with my jumper source. Solenoid 4 measured 2.1 amps, far different from the 0.174 it should have been. I also checked solenoid 6 with pin 58 and pin 22 using a fused jumper, and it measured 2.4 amps, within range. Now that I had confirmed that solenoid 4 was out of specification and there was low voltage from the TCM, I determined that I had two problems to address. I tested the solenoids at the transmission connector to make sure there was no issue between the transmission and the TCM. The test was a carbon copy of the test at the TCM. The valve-body cover had to come off.
I ordered a solenoid to have on hand once the cover was off. I inspected the work that was performed previously and thought, “How could the solenoids have been replaced and there is still a bad solenoid?” I identified the solenoid locations, and to my surprise solenoid 4 had been replaced with an EPC solenoid. That explained the low resistance reading, the high amperage and the trouble code. While the pan was off I visually checked the other solenoids to make sure they were in their correct locations. Could this have damaged the TCM, or was it like that before? I installed the correct solenoid and retested, and the solenoids were working correctly now.
Now it was time to reconnect the TCM. With the TCM reconnected and key on, engine off, I was still getting a code for solenoid 6. I back-probed pin 1 again, looking for B+, and still found low voltage. I concluded that the TCM had failed. I ordered a TCM, installed it and scanned for codes, and there were none. I road-tested the vehicle and the transmission worked correctly.
I’m not a VW specialist by any means; in fact, this was one of the first ones on which it I got in depth. What really helped was a good knowledge of electrical components and the ability to read schematics. The VW schematics, in my opinion, are very easy to follow.
Randall Peterson has been with Certified Transmission for more than 20 years and has done it all – building transmissions, diagnosing cars and running a store.