Do you shy away from customers that come to you with a transmission complaint? Today, nearly everything on the car is electronically controlled, and the transmission is no exception. Sometimes, as POWERTRAIN PRO publisher and ATSG President Wayne Colonna shares, problems on the drivability side and cause issues on the transmission side, and vice versa.
Recently, two vehicles came in to the Car Clinic bays (home of our TST webinars and the classrooms of ATTS) with tranny complaints. Let’s learn right along with lead tech Alex Portillo (who shares his experiences here) and perhaps you’ll be less reluctant in the future.
First, a 2003 Volvo S60
Before I get started telling you about the transmission problem, I would like to share my memory of this vehicle with you. It might be helpful information should you experience the same problem. This Volvo was in about six months earlier with an owner complaint of the instrument cluster not working. While performing my diagnosis, I found that all vehicles systems were Diagnostic Trouble Code (DTC) free and the only problem was a cluster that was dark and not working.
.jpg?auto=format,compress&fit=max&q=45&w=250&width=250 "undefined")
This Volvo customer was one we all have, a price shopper looking for the lowest cost.
With an AutoLogic scan tool attached, I was able to communicate with the cluster, but the dash gauges and lights would not work. I also should tell you that beside the gauges and lights, this cluster utilizes an information display that also was not operational. We suggested to the vehicle owner a new cluster and cluster configuration in order to get everything back to normal, but the vehicle owner declined to repair the vehicle.
Moving on to why I had this Volvo back in my service bay was for a new customer concern of a transmission shifting problem. The first thing I noticed was that the cluster was now working but the dash information window had an SRS (restraint system) message displayed. (Remember this information as you read on about the transmission shifting problem.) My diagnosis started with a test drive along with a scan of the vehicle computers to see if it would reveal any clues leading to the transmission shift problem.
This Volvo looked like it was going to be difficult to diagnosis, because the owner replaced the dash cluster with a used part at a different shop and likes to bounce from shop to shop, looking for the cheapest estimate. (That never happens, right?) Suddenly I realized that this problem was not going to be as bad as I thought, because the transmission expert, Colonna, was in the building.
.jpg?auto=format,compress&fit=max&q=45&w=250&width=250 "undefined")
Whenever I’m faced with a diagnostic problem, I like to check all the modules for codes.
He was up here working with TST on a webcast called “Driveability Meets Transability” (editor’s note: you can see the webinar in its entirety on the TST YouTube channel or in the Motor Age AutoPro Workshop), so today really was going to be my lucky day with expert help in the house. Because I don’t rely on others to diagnosis problem vehicles for me, I decided to proceed with my diagnostic game plan. Without any assistance I continued on and found that this Volvo had the following problems; hard shift going into drive, late 2-3 shift, along with a loss of drive for a few seconds.
I checked for Technical Service Bulletins (TSBs), made sure that the Transmission Control Module (TCM) had the latest flash and that there were no transmission or engine DTCs. I scanned the complete vehicle and located an ABS and SRS DTC, not thinking that I had to be concerned with them since they are not normally the cause of a transmission problem. My first plan of action was to perform a TCM adaptation, knowing that my previous experience for this type of problem was resolved by doing so.
When I connected the AutoLogic scan tool to perform the TCM adaptation, it did not progress as it usually does, and I wasn’t sure if it was working or not. While I was in the process of the adaptation, Colonna came out into the shop and asked me what was wrong with the Volvo. I explained the shifting problems to Wayne and told him that I was concerned about the adaption process because it displayed “Active” on the screen for longer than normal. He suggested that I clear the DTCs from the ABS and SRS then try the Adaptation again.
.JPG?auto=format,compress&fit=max&q=45&w=250&width=250 "undefined")
Luckily, Wayne Colonna was in town when I had this Explorer to diagnose.
The transmission expert was right. In this instance, you can’t have any active DTCs present while performing an adaption. After I cleared the DTCs and message on the cluster I tried the TCM adaptation again. Now successful, the transmission problems were resolved along with the SRS DTC. It was a different story for the ABS DTC that came back on during the test drive. So the moral of this story is that any DTCs or messages in the instrument cluster display has to be repaired (for the Volvo anyway) before the vehicle is able to accept a TCM adaptation.
Next, a 2001 Dodge Dakota
While Colonna was in town, I had another problem vehicle, this time a 2001 Dodge Dakota 4x4 3.9L V6 with a 42RE transmission. It came in with a complaint of a hard first shift. I started my diagnosis with a scan of the vehicle computer systems (I do this on all of my diags) and came up with only a rear oxygen sensor code PO136 (O2 Sensor Bank 1 Sensor 2 heater malfunction).
.JPG?auto=format,compress&fit=max&q=45&w=250&width=250 "undefined")
Even though this cable had popped off, the shifting problem wasn’t corrected until I fixed the O2 heater code.
Colonna, being the helpful guy he is, explained to me that the oxygen sensors on some vehicles might share feeds that have a connection to the transmission. He went on with his explanation in more detail, saying that if there is a problem with one of the oxygen sensors it could affect transmission shifting. I decided to take a look at the wiring schematics and trace the wiring to see if they share any connections.
After tracing through the wiring, I told Colonna that I was not able to find any shared connection. He continued on with his explanation, telling me that the system internally shares something in common on the multiplex circuit. My next step at this point was to disconnected the oxygen sensor wiring and take it for a ride to see if the shifting problem still existed. Unfortunately the shift problem was still present, having me second guessing myself, thinking that I might have done something wrong, but what?
I pulled the Dodge back in and lifted it up taking another visual of the transmission and O2 wiring, only to find that the shift cable for 1st and 2nd gear was not connected. I guess when I replaced the transmission a few months back, I probably did not press the shift rod clip in all the way and it worked its way loose. I now clicked it back in place and took the vehicle for another test drive to see if the transmission shifted correctly. End of story?
By now you might be thinking about the explanation of the O2 sensor circuit causing the problem. Well, being the curious tech I am and knowing that Colonna knows transmissions inside and out, I decided to reconnect the bad O2 sensor wiring and go for another test drive. The result of this test drive was that the shifting problems were back again, confirming that there was a relationship between the O2 heater circuit and transmission. I finally fixed the vehicle when I replaced the O2 sensor, and confirmed the repair by performing a test drive and until the O2 Heater Monitor completed.
Subscribe to Motor Age and receive articles like this every month…absolutely free. Click here
