My 2001 tracker is dropping out of 4 wheel drive. Removed the actuator and did the following. Dissembled oiled slightly. No rust or debris inside. Tested on bench actuator moves and pump will pump on bench but seems weak. Tested car side of wiring. Getting 11.5v on pump wire and 10.33 on actuator side whether it is in 4 wheel drive or not . Connect wire to pump/actuator and nothing. Any suggestions?

 

When the actuator was on the bench, did you connect +12 volts to pin 3 (red) and battery negative to pin 2 (black)?
If yes, did the pump motor run?
If no, did the pump motor run when pin 1 (pink) was momentarily (no more than 10 seconds) jumpered to pin 2?

 

Yes. It ran when black, (negative) was connected and the 1 red pin. But it ran very slowly.

 

After crawling under my 2001 Tracker with a logic probe I realized I had been operating under a couple of misconceptions. The Suzuki prints were drawn wrong in the conversion from a separate 4WD controller (1999 & 200) to PCM control (2001). Pin 3 is LOW with the key ON but goes HIGH when the lever is moved to 4WD. That voltage from the PCM simultaneously closes the (normally open) pressure relief valve and starts the pump motor. I also carried a battery and jumper wires under the car to recreate your bench test. The motor ran a soon as the battery was connected to pins 2 and 3. After three seconds the pressure switch opened and the motor stopped. The pressure bled off (because I had a leaky pump) and the motor restarted. That cycle continued until I disconnected that battery. On the bench the motor will not shut off unless you block the air outlet or connect a pressure gage (more on that later). It is important not to overheat the pump on the bench by running it for more that ten seconds at a time. I have modified my theory of operation and am reposting it here. PCM pin numbers refer to the V6 engine only.

 

I have corrected my theory of operation above and am posting the instructions for bench testing the actuator pump here.

 

I like a puzzle but this 4WD actuator pump had me going in circles. I spent the morning on the Suzuki Forums https://www.suzuki-forums.com/thread...fo-here.24778/ looking for clarity. What I found instead was a mix of test results, questionable interpretations and some explanations that don't hold up under scrutiny. I waded through the truth, half-truths and conjecture in an attempt to find an explanation consistent with Ohm's law, the hardware in the car and the required 4WD functions.

Max said, "You CAN hear [the pump] run momentarily when you shift to 4WD, with the key on (engine off)..."

I checked this on my car and it is absolutely true. The motor runs for about three seconds and shuts off.

Transalper said, "1. If it runs/pumps when the 4wd lever is shifted (key in ignition) and runs for ten seconds and then stops, there is a leak in the system. 2. If it runs/pumps for a second or two, it is functioning properly.

This is also true. the PCM shuts the pump motor off after ten seconds to prevent overheating if there is an air leak in the system.

Transalper goes on to say, "The 4wd light is activated when the pressure sensor in the pump reaches the proper level."

This is true. The 4WD light illuminates when the pump reaches the proper pressure but that happens because the internal pressure switch opens the ground path back to pin 18 of the PCM (2001 model year, 2.5L).

Visoundguy said, "My pump won't come on at all - but there is a click in the actuator, and the light turns on! So if the pump isn't running, the light is not turned on by the pressure!"

Visoundguy caught some flack for this but he is half right. The 4WD indicator will light if the pressure switch opens due to air pressure or stuck open because it's broken. My 4WD indicator came on when the 3-wire actuator connector was unplugged. Pin 18 on the PCM saw no ground so it assumed (wrongly) the pressure was good and the 4WD was engaged.

Visoundguy goes on to say, "I checked the three-pronged electrical plug that this pump plugs into and see that there appears to be one power wire - and 2 grounds (returns)."

This is almost correct. Pin 3 is the power feed. Pin 2 is a permanent chassis ground and pin 1 is the pink wire that sends the pressure switch signal back to pin 18 of the PCM (2001 2.5L V6).



I could not understand why the factory PCM schematics showed a transistor switch at pin 18. After months of research and experimentation I realized the Suzuki and Chevy schematics have the PCM internals at pins 15 and 16 reversed. Pin 15 of the PCM is a transistor switch with the collector connected to 12 volts (as shown above). Pin 18 has a pull-up resistor internally tied to 12 volts as well. The 4WD lamp in the dash stays OFF as long as pin 18 is grounded. When the pressure switch removes the ground from pin 18, the 4WD drive lamp illuminates. Pin 15 is an output from the PCM. Pin 18 is an input to the PCM.

Back to Visoundguy. "If I put 12V across the power and one of the terminals, I get the click - if I apply 12V across the power and the other terminal, the pump runs!"

That makes perfect sense. When he applies 12 volts across pins 3 and 2 he gets a click. That's because his defective pressure switch is stuck open. The click is the solenoid coil closing the Normally Open pressure relief valve. The motor refuses to run because it's current path to ground (pin 2) is open. When he applies 12 volts across pins 3 and 1 the motor runs because that path for current does not run through the pressure switch. However, without a ground at pin 2 the relief valve will stay open and pressure can never build up.

AMforman says, "If the system builds pressure in less than 10 seconds the pressure switch opens and removes the ground from the pink wire which stops the motor and tells the control unit you are up to pressure."

This is true. The open pressure switch removes the ground to the pink wire and tells the 4WD controller the differential is up to pressure. Starting in model year 2001 the 4wd controller was replaced by the PCM. The PCM operation is functionally the same and the 4WD controller operation but the internal switch is solid-state rather than a electro-mechanical relay.

AMforeman goes on to say, "Put ground on the black wire and 12v on red wire. If the pump runs the pressure switch is good. If not, the pressure switch is bad..."

This is potentially wrong twice. The pressure switch could be stuck closed (defective) and the motor will run (but will never shut off). If the motor doesn't run it could be a bad motor and not the pressure switch. The motor can be tested independently from the pressure switch by applying voltage from pin 3 to pin 1.

WVkartracer said, "my pump runs with pink and red connected but only "clunks" when red and black are connected."

This is the same problem Visoundguy had: a defective (stuck open) pressure switch. This is what the service manual bench test tests for.

Fordem said, "when the system is successfully pressurized, a microswitch inside of the pump opens and in response, the compressor is turned off and the pink wire to the PCM goes low (0V) to signal the PCM that the system is properly pressurized."

Fordem is correct that the opening of the pressure switch shuts off the pump but technically the pink wire goes to 12 volts (due to the PCM's internal pull-up resistor). Zero volts (ground) on the pink wire turns the 4WD indicator lamp OFF. 12 volts on the pink wire turns the indicator lamp ON.

The errors in the Suzuki manuals were copied over to the Chevy manuals. The bottom line is that pin 15 is a PCM output and pin 18 is a PCM input.

 

Continuing to investigate this puzzle I found a video of a guy rebuilding a Tracker actuator pump. It's little long but it let's you see inside the pump without taking yours apart.


Then I learned that the Kia Sorento and Jeep Wrangler (with a Dana 44) uses the same pump. See video here:


But the most interesting thing was information I found on this webpage:

Test Actuator Pump, Air Pump, Vacuum Pump Chevy Suzuki kia Jeep

The author says, "A good Air Pump should put out between 5.4 - 8.2 PSI on a pressure tester and then hold it for three minutes."

That worrisome because my pump only held pressure for about 3 seconds when I tested it on the car. That means either my pump is leaking or my front differential has a leak. It should not be hard to figure out which is the problem.

The other thing that got my attention was this:

"Kia changed from a 3 prong to a 2 prong somewhere about 2006. The pump is still the same with three prongs, however the vehicle side of the plug eliminated a prong and is now only power and ground. So, what that means is the 4 WD indicator light messaging has moved. Otherwise said, the pump is capable of sending a message to the 4 wheel drive indicator light, however Kia has eliminated that function and opted for a message sent from a location inside the differential carrier, arguably a more true reading."

 

Yeah I watched that first video before I took mine off. I wish it showed how he tested it. I just ordered a new pump. Hopefully it fixes the problem. Thanks.

 

If you mean tested it on the bench after he replaced the O-rings, I don't think he did. I was hoping he would but I think he just hooked up to the car and verified that the 4WD indicator illuminated.

 

My 4wd indicator has never gone off if I have it in 4wd. Doens't blink either. The 4 wd just doesn't work.