8 GEARS September 2006

IIn the first part of this series we covered a few of the dif-ferences between the A4AF3/A4BF2 transaxle that uses 6-solenoids, and the earlier 4-solenoid version used by

Hyundai from 1993 – 1999. The newer version adds two new solenoids (shift solenoid C and pressure control solenoid B) that improve transaxle performance, but with them came a few quirks.

Let’s continue looking at some of the differences you’ll face with this newer KM transaxle. To begin with, Hyundai eliminated the idle switch, sometimes referred to as a closed throttle switch. This switch was used so the transaxle would only shift down to second gear during a stop. This was referred to as creep mode. This feature was somewhat problematic when the switch was out of adjustment, causing a clunk during a coast downshift. Hyundai eliminated this problem altogether by shifting 3-1 on the coast downshift (at about 3 MPH). Because of this, there’s no longer a need for the switch.

Another change they made with sensors and switches occurred in 2003 with the change to a Hall Effect VSS (figure 1). The earlier VSS was a reed switch mounted in the speed-ometer. Both create a square wave signal, so as far as the computer is concerned nothing changed. The remainder of the sensors and switches used on the 6-solenoid transaxle are the same as the earlier 4-solenoid version and all the other KM series units you’ve come to know and love, so their functions and the tests for them are the same.

The KM series transaxles, including the Hyundai variet-ies, have all used a separate TCM (transaxle control module)

and an ECM (electronic control module). This version fol-lowed suit until 2003, when they combined the two modules into a single PCM (powertrain control module). The 2000 through 2002 TCM was a modified version of the 4th design module, introduced by Mitsubishi in 1994 and used by Hyundai beginning in 1995.

The six-solenoid version looks identical to the 4-sole-noid version, so be sure you’re buying the right TCM for the vehicle you’re working on. On top of that, the PCM, which controls both the engine and transmission on 2003-and-later models, looks the same as the 2000 – 2002 ECM used in the Accent; the ECM just lacks the transmission control circuitry.

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Those Darn KMs:Those Darn KMs: SPEAKER

by Dennis MaddenHyundai Takes Hyundai Takes a U-Turn;a U-Turn; The Sequel The Sequel

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10 GEARS September 2006

Again, make sure you’re buying the right one.Now for some electrical testing: These cars

have a light on the dash that comes on when the TCM or PCM detects a transaxle-related problem (figure 2). There are a couple of problems with this system: not everything sets a code, including problems where a code actually exists. This isn’t uncommon and is often because your scan tool is incompatible.

On earlier cars with the KM series transaxle, you could retrieve the codes manually with a voltmeter (fig-ure 3). The 2000 model was the last year Hyundai made this available, so after that you’re stuck if your scan tool won’t work. We covered the entire procedure for manual code retrieval in the December 1997 issue of GEARS, so if you’re working on a 2000 model, try that method.

Obviously, these units will have additional codes for the two extra solenoids, and oddly, Hyundai eliminated a few codes. Figure 4 shows a list of the valid codes for 2000 – 2006 models. As I mentioned, getting a code for an electri-cal or dynamic failure has never been too reliable. And the code symptoms don’t always work. For example, an open circuit in either of the pulse generators is supposed to put the system into failsafe. But it can also cause no shifts, keeping the transaxle in first gear.

No reverse? How about a bad range switch? I’ve seen the switch fail, cause no reverse and not set either of the two codes assigned to it: P0707 and P0708. I’ve also seen the range switch fail where it didn’t report Drive to the PCM and cause a harsh drive engagement with no overdrive, and, you guessed it: no codes.

Look, make things easy on yourself: This system needs

very little sensor information to work right. Make sure the range sensor works, the pulse generators aren’t swapped and the connection is good, and the servo switch works; that’ll resolve 80% of all computer-related issues. All of these sys-tems are the same as earlier versions, so we won’t go into them in detail.

Next, let’s take a quick look at the valve body (figure 5). With the exception of two additional solenoids it looks just about the same as the 4-solenoid version. Figure 5 also shows the position of each solenoid and its wire color. And just like its predecessor, it has an adjustment for reducing pressure which controls shift feel (figure 6). As before, adjusting the screw clockwise softens the shifts; counterclockwise makes the shifts firmer.

This transaxle is just like any other KM with a couple of quirks. Use the information here to help fill in the blanks and you’ve got it made. In our next and final installment in this series, we’ll go really deep into the hydraulic differences in this unit that you just can’t live without knowing. We’ll go through some of the failures you can expect, and make understanding it a snap!

Hyundai Takes a U-Turn; The Sequel

Figure 5

DTC Code Defi nitionP0707 Inhibitor Switch; No Signal

P0708 Inhibitor Switch; Multiple Signals

P0711 Trans Fluid Temp Sensor Circuit Out of Range

P0712 Trans Fluid Temp Sensor Circuit Shorted

P0713 Trans Fluid Temp Sensor Circuit Open

P0717 Pulse Generator A Circuit Open

P0722 Pulse Generator B Circuit Open

P0731 Ratio Problem in 1st Gear

P0732 Ratio Problem in 2nd Gear

P0733 Ratio Problem in 3rd Gear

P0734 Ratio Problem in 4th Gear

P0741 Damper Clutch Stuck Off

P0742 Damper Clutch Stuck On

P0743 Damper Clutch Solenoid Circuit Problem

P0745 Pressure Control Solenoid A Circuit Shorted

P0750 Shift Solenoid A Circuit Problem

P0755 Shift Solenoid B Circuit Problem

P0760 Shift Solenoid C Circuit Problem

P0775 Pressure Control Solenoid B Circuit Shorted

P1703 Throttle Position Sensor

P1709 Kickdown Servo Switch Open or Shorted

P1744 Damper Clutch; Abnormal Vibration

P1765 Torque Reduction Request Signal Lines

P1766 Torque Reduction Request Signal Lines

Figure 6

Figure 4

SSC(White)

PCB(blue)

PCA(black)

DCS(red) SSB

(brown)SSA

(yellow)

Reducing pressure adjustment

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