Hi , I am new to this forum so bare with me. I have a 2003 h2 with service 4wd light on the dash. I scanned it and it had the codes c0388 and b0790.Everything works but the locker. I disconnected the plug from the rear end and did an Ohms test,03.3 ohms across the locker coil. i know it is suppost to be between 2.2 and 4.3.Where would I look now????
Thank you in advance

 

Anybody, this is driving me nuts!!!

 

Is the locker bad?

 

I'm not sure but I don't think so, The code c0388 means something is wrong with the electric going to the locker.I tested the coil and I'm not sure if the ohm reading means it's good or bad.

 

Is the ohm reading under load?

 

No I disconnected the tab connection to the rear end and took a reading from the two prongs going in to the rear end. Completely isolated from the rest of the truck.

 

Still can't find the problem, can anybody help. I replaced the tranfercase selector switch in the dash and still have the same problem.

 

Trouble shoot idea:

Jack up the rear end and put the truck in neutral so you can spin the rear tires while they are off the ground.

Check the power source voltage needed to operate the locker, assuming it is 12 volts, run a separate wire from the battery or another source directly to the prongs in the differential housing.

Turn the rear wheels manually, if they both turn the same way, the locker works, if they turn opposite directions when you turn one then the locker is off and it functions as a open differential.

Now switch the polarity of the wires (put the wires on the opposite prongs) and try again.

If the wheels don't turn together then your locker is bad. If they do then the wiring from the locker back is bad.

Sound reasonable to everyone else here?

Just thinking aloud

Ross

 

DTC C0388

Circuit Description

The rear differential control circuit consists of an actuator which engages and disengages the rear axle differential lock. The rear differential actuator consists of a coil assembly, and a locking assembly with springs and pins to lock the rear differential, all within the rear differential assembly.

The rear axle differential lock actuator consists of the following circuits:

• The rear differential lock control circuit, which is connected to the transfer case shift control module and supplies battery voltage.
• The rear differential lock return ground circuit, which is also connected to the transfer case shift control module.

Whenever the rear differential lock has been requested the transfer case shift control module provides battery voltage through the rear differential lock control circuit, and provides ground through the rear differential lock return circuit through a current limiting driver.

Whenever a rear differential lock is requested the transfer case must be in 4 LO and the vehicle speed must be below 5 km/h (3 mph) for the request to be accepted. The rear differential lock will remain locked up to 32 km/h (20 mph) after which the rear differential lock will disengage.

This DTC detects a short to ground, short-to-voltage, or an open circuit.

Conditions for Running the DTC

• The ignition is ON.
• The system voltage is 9-18 volts.

Conditions for Setting the DTC

• The transfer case shift control module monitors the state of the rear axle differential lock actuator. The transfer case shift control module reads the rear differential lock control, and the rear differential lock return circuits for a high and low voltage. The DTC will set if these circuits are high when a low voltage is expected or when the circuits are low when a high voltage is expected.
• The DTC will set if this circuit is high when a low voltage is present or when the circuit is low when a high voltage is present.

Action Taken When the DTC Sets

• All rear differential lock requests will be disabled. Transfer case mode shifts will not be affected.
• SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.

Conditions for Clearing the DTC

• The Transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present.
• A history DTC will clear after 33 consecutive ignition cycles without a fault present.
• History DTCs can be cleared using a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines of the coil has excessive resistance or if the windings are shorted together.
3. This step determines if the coil or pigtail is shorted to ground.
4. This step determines if either the differential lock control or differential lock return circuits are shorted to ground.
5. This step determines if the differential lock control and differential lock return circuits are shorted together.
6. This step tests for an open or high resistance in both the return and control circuits.
7. This step refers to transfer case shift control module replacement.
8. This step refers to encoder motor replacement.

 

DTC B0790

Circuit Description

The Neutral indicator circuit consists of a ignition 3 voltage circuit and a Neutral indicator control circuit. When the Neutral mode has been selected by the driver, current is supplied to the Neutral indicator by the ignition 3 voltage circuit, traveling through the Neutral indicator LED at which time the transfer case shift control module supplies the ground through the Neutral indicator control circuit. This DTC indicates an open, short to ground or a short to voltage.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0790 Transfer Case Neutral Indicator Circuit Malfunction

Conditions for Running the DTC

• The ignition is ON.
• The system voltage is 9-18 volts.

Conditions for Setting the DTC

• The system monitors the voltage on the Neutral indicator control circuit.
• If the system detects a voltage 3.5 volts or less when the Neutral indicator is not commanded, the DTC is logged.
• If the system detects a voltage 3.5 volts or more when the Neutral indicator is commanded, the DTC is logged.

Action Taken When the DTC Sets

The SERVICE 4WD indicator will remain illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC

• The transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present.
• A history DTC will clear after 33 consecutive ignition cycles without a fault present.
• History DTCs can be cleared using a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests for voltage at the ignition 3 voltage side of the transfer case select switch.
3. This step tests the control circuit of the Neutral indicator for a short to voltage or an open.
4. This step tests the control circuit of the Neutral indicator for a short to ground.