In this issue of Keep Those Trannys Rolling, we’re going to look at the 2015 Honda CRV all-wheel drive systems and what it takes to keep them rolling down the road.
The 2015 Honda CRV is equipped with a 2.4L engine, a continuously variable transmission (CVT), a power transfer unit, and either a dual pump system (DPS 4WD), rear differential assembly, or an electronically controlled coupler system (ECCS AWD) rear differential assembly.
While each of these systems uses a power take-off unit (PTU) attached to the CVT, the differential assemblies are completely different from each other. Now, let’s take a moment to get a better understanding of how each of these systems operates.
THE DUAL PUMP SYSTEM (DPS 4WD)
The Dual Pump System uses a mechanically controlled differential that allows most of the transmission driving force to be distributed to the front wheels and then transmits the appropriate driving force to the rear wheels as needed.
The DSP (figure 1) differential consists of:
- A rear differential carrier assembly
- A torque control coupler assembly
The rear differential carrier assembly (figure 2) consists of:
- The differential housing
- The hypoid drive pinion gear
- A ring gear
- A carrier assembly
- Carrier bearings
- Seals
The torque control coupler assembly (figure 3) consists of:
- The torque coupler differential (TCD) case
- An oil bath clutch assembly
- A one-way cam
- A front and rear oil pump assembly
DPS FOUR WHEEL DRIVE SYSTEM OPERATION
The dual pump four-wheel drive system uses a front and rear oil pump (figure 4) to control the amount of torque going to the front and rear wheels.
When the difference between the front and rear wheel speeds are minimal (no slip), the amount of oil discharged by the front pump is equal to the amount of oil drawn by the rear pump, so the oil bath clutch assembly isn’t engaged so it doesn’t send torque to the rear wheels. This puts the system into 2WD.
When the front wheel speed exceeds the rear wheel speed, the amount of oil discharged by the front pump exceeds the amount of oil drawn by the rear pump. This creates pressure, engaging the oil bath clutch, which sends torque to the rear wheels. This puts the system into 4WD.
The DPS 4WD system is mechanical, so it doesn’t require electrical system diagnosis.
ELECTRONICALLY CONTROLLED COUPLER SYSTEM (ECCS AWD)
The electronically controlled coupler system (ECCS AWD) uses an electronically controlled differential that controls the amount of torque going to the front and rear wheels.
The ECCS AWD system is equipped with a motor-driven oil pump and electronically controlled valves that allow for a wide range of torque control to the rear wheels.
The ECCS AWD differential system consists of:
- A rear differential assembly
- An electronically controlled coupler assembly
- An AWD control module or control unit
- Wiring and connections
The rear differential consists of:
- The differential housing
- The hypoid drive pinion gear
- A ring gear
- A carrier assembly
- Carrier bearings
- Seals
The electronically controlled coupler consists of:
- An ECCS torque coupler case
- An oil pump
- A wet clutch assembly
- A one way valve
- A pressure relief valve
- A differential solenoid valve
- A differential fluid pressure sensor
- A differential fluid temperature sensor
ECCS ALL-WHEEL DRIVE SYSTEM OPERATION
The ECCS AWD System is controlled by a device called either an AWD control module or AWD control unit (figure 5). This device uses shared information from the powertrain control module (PCM), the vehicle stability control module (VSA), the antilock brake control module (ABS), the gauge control module (GCM), and the steering angle sensor to control the AWD system. The AWD control module uses this shared information to calculate how much torque needs to be transferred to the rear wheels.
The AWD control module monitors the ABS system front and rear wheel speed sensors to determine if the front wheels are slipping, the PCM for load inputs, and the steering angle sensor to control the electronically controlled coupler assembly (located on the rear differential assembly).
If the AWD control module encounters excessive front wheel slip, load (hard acceleration), yaw rate, or vehicle tilt (driving on a steep grade), it’ll engage the AWD system.
DIAGNOSING THE ECCS AWD SYSTEM
Diagnosing the ECCS AWD system requires a compatible scan tool to retrieve codes and monitor various inputs from the powertrain control module, the vehicle stability control module, the antilock brake control module, the gauge control module, and the steering angle sensor.
Codes or problems in any of these systems can cause erratic AWD system operation. If the all-wheel drive system encounters a problem, the AWD control module will light the AWD light, located in the instrument cluster (figure 6).
CHECKING ECCS AWD SYSTEM FOR CODES
Checking for codes in all modules is simple: Just connect your compatible scan tool to the vehicle DLC and check each onboard module for codes, one at a time.
Repair all codes in other modules before attempting to diagnose the AWD system. Codes in other modules can interfere with the AWD system operation.
Figure 7 shows a list of codes you may find in the AWD control module.
ECCS AWD SYSTEM WIRING SCHEMATIC
Diagnostic routines for these codes appear in the appropriate service manual, or you can contact the ATRA Technical Hotline for diagnostic procedures and wiring schematics.
Well, there you have it. We’ve examined the 2015 Honda CRV 4WD and all wheel drive systems and discussed each system’s operation.
With a better understanding of Honda’s 4WD and all-wheel drive systems, you should have no problem keeping those systems rolling down the road.
