This bulletin is being revised to include 2006 model year, to enhance the Auto Start/Stop and Battery Charging sections and provide essential tool information. Please discard Corporate Bulletin Number 04-00-89-020A (Section 00 -- General Information).
Important: It is strongly recommended that technicians complete the available Hybrid Truck training and have the essential tools available to service a Hybrid truck.
The purpose of this bulletin is to make you familiar with the Hybrid Truck option. In addition, this bulletin will review critical safety precautions and describe specific action that your Service Department will need to take to ensure that you are able to fully service this exciting new product.
Technicians should complete GMSTC course # 18050.01W -- Silverado/Sierra Hybrid Truck: Theory, Operation and Service, and pre-requisites, prior to working on a Hybrid truck. Refer to the www.gmtraining.com website for details. In Canada, the course number is # 18050.03.
The following safety precautions should be observed while working on a Hybrid Truck:
Caution: Never leave the ignition key in the ON position without disconnecting the 42V service disconnect switch. The hybrid system may become active and start the engine when you least expect it.
Caution: To reduce the risk of severe shock and burns, disable the 42 volt (42V) system anytime you perform service work on or around the energy storage box (ESB). The 42V system will still be active after you have disabled the ESB. To disconnect the ESB, turn the engine off and turn OFF the service disconnect switch, which is located on the passenger side of the ESB.
Caution: To reduce the risk of severe shock and burns, always treat the 3 phase cable and connectors as if voltage is present and as if the surface of all parts of the cable is hot.
Caution: De-energizing the supplemental inflatable restraint (SIR) system in a 12 volt vehicle requires disconnecting the negative battery cable before disconnecting the positive battery cable. The 42 volt system must be disconnected to fully neutralize the supplemental inflatable restraint system (airbag).
Caution: The hybrid truck is equipped with an automatic stop/start feature. This feature will cause the engine to turn off if the vehicle speed is less than 21 km/h (13 mph), or when the vehicle comes to a complete stop. Special precautions should be taken under the following circumstances: • If you are in the vehicle and come to a complete stop, the engine will stop. However, if you open the door and remove your foot from the brake, the engine will start and it is possible the vehicle can move forward. Place the shifter in Park and turn the ignition to the lock position before exiting the vehicle. • If the vehicle is on an incline, the vehicle may roll backward a short distance until the engine performs the auto start. To be sure the vehicle will not move or roll, always keep your foot firmly on the brake pedal until you are ready for the vehicle to move.
Caution: The hood ajar switch communicates whether the hood is open or closed. The engine cannot auto start if the hood is either ajar or open. This ensures that the engine does not start unexpectedly when someone is servicing the vehicle. The engine can always be started using the ignition key if the shift lever is in NEUTRAL or PARK (P). Note, the hood can be opened after the engine is running and the engine will remain running, as with other vehicles.
The Hybrid Option (RPO HP2) is offered on both two-wheel and four-wheel drive Silverado/Sierra fullsize extended cab pickup trucks. The hybrid option provides built-in generator capability and results in improved fuel economy and reduced carbon dioxide emissions as compared to other GM pickup trucks. The hybrid option has the following features:
This feature causes the engine to turn off while braking if the vehicle is going less than 21 km/h (13 mph), or when the vehicle comes to a complete stop. When the brake pedal is released, the engine will start again and the vehicle will continue forward.
The engine will stay running at a complete stop or will automatically start from a complete stop if the following apply:
The Auxiliary Power Outlet system provides up to 2,400 watts of 120 volt AC power. If equipment is used that requires more than the limit, a 20 amp protection circuit will cut the power supply and a light in the APO switch will flash along with a Driver Information Center (DIC) message that will flash 120V OVERLOAD. If this occurs, the system must be reset. Refer to SI Document ID #1325743.
The APO has two modes:
The conventional power steering pump has been replaced with a 42-volt electro-hydraulic power steering powerpack (p/n 15270264 -- p/s pump). The EHPS powerpack includes a 42-volt motor, electronics/circuit boards, fluid reservoir, and pump. The EHPS powerpack controls the power steering motor, which has the function of providing hydraulic power to the brake booster and the steering gear.
The hybrid control module acts as a gateway between the high-speed GMLAN and Class2 network. The HCM controls the following functions:
the automatic engine auto start/stop
the energy flowing into/out of the 14 volt and 42 volt batteries
enables and disables power for the auxiliary power outlets
enables and disables surge smoothing/active dampening
disables energy generation after airbag deployment
controls the auxiliary transmission pump, the power maintenance relay, and the auxiliary heater pump
controls the starter/generator speed during transmission downshift assists
The following is a list of key components that make up the Hybrid system:
The 4L60-E M33 model transmission is specifically designed for the Hybrid pickup trucks. The starter generator includes a rotor (2) and stator (1) housed inside the transmission torque converter housing (5). The stator (1) is attached to the engine block, and the rotor (2) bolts directly to the engine crankshaft and spins inside the stator.
The starter generator and a 258 mm (10 in) torque converter (4) are mounted between the engine and transmission (6). The torque converter is attached to a unique flex plate (3) that fits inside the rotor (2).
The M33 secondary oil pump ensures sufficient line pressure is available immediately to transfer torque when the engine is restarted, avoiding delayed or loss of forward clutch engagement during transition to main pump oil supply.
Also unique to the M33 is the torque converter clutch lockup that occurs very early. Once locked, the converter smooths out driveline disturbances and provides coast-down regenerative braking. The torque converter clutch engages (or, in some instances, permits a controlled, very low slip mode) in second and successive gears to help prevent any additional pump and turbine heat buildup.
During periods when the engine is not running, a secondary oil pump (1), Figure 2, mounted to the valve body (2) provides the necessary fluid to slightly apply the forward clutch. This gives the transmission the ability to maintain forward clutch capacity to ensure rapid clutch engagement during the engine restart cycle, eliminating engine flare or sudden transmission engagement during transition to main pump pressure. The secondary fluid pump provides fluid directly to the manual valve. The pump is controlled by the Hybrid Control Module (HCM) through the Auxiliary Pump relay. The secondary pump assembly is NOT repairable. If the pump needs repair, it must be replaced.
A one-way check valve (1), Figure 3, installed in the valve body prevents hydraulic fluid flow to the secondary pump when the main oil pump is operating.
The M33 Transmission Fluid Pressure (TFP) switch (1), Figure 6, is specifically calibrated to recognize lower fluid pressure from the secondary fluid pump assembly.
Important: The M30 and the M33 TFP switches are not interchangeable and can be distinguished by the color of the electrical connector.
The M33 TFP Switch has a natural color electrical connector, where the M30 has a black connector. The D4 switch of the TFP is specifically calibrated to detect secondary fluid pump pressure.
Figure 7 shows components that mainly comprise the M33 model.
The M33 transmission model can be identified by the broadcast code label (1), Figure 8. The M33 is identified as 4PCD and 4PKD models.
With the Auto Start/Stop feature, customers may comment on a delay in vehicle acceleration from a complete stop. This is a normal characteristic of the vehicle. Because the vehicle engine shuts off while at a complete stop, when the brake pedal is released, the starter/generator engages to start the engine before the vehicle can accelerate. The customer may realize a slight delay while this occurs.
Also, with the auto-stop feature, the customer may feel a "bump/bobble" when the engine shuts down. This is caused by the PCM setting up the engine pistons to a specific position for the restart.
The power steering system in your vehicle differs from a traditional vehicle. The electro-hydraulic power steering (EHPS) powerpack uses a 42V electric pump to produce hydraulic pressure for steering and brake assist, rather than a belt driven pump coupled to the engine. You may hear the sound of the electric motor when operating the vehicle, particularly if the windows are down. Some audible sound from the EHPS powerpack is considered normal, and is expected in a system of this type. Excessive noise, however, may indicate a need to check the level of power steering fluid.
Regenerative braking works when you take your foot off the accelerator pedal and the vehicle is moving in DRIVE (D). Regenerative braking will cause the vehicle to slow down faster. Customers may comment on a "drag" feel or as if the brake pedal is being depressed.
Regenerative braking is accomplished by applying the overrun clutch during vehicle coast-down and braking. With the transmission in second or third gear, the overrun clutch is applied. This allows power to be transferred back through the transmission torque converter to the starter-generator.
The M33 utilizes a bonded spacer plate assembly, consisting of a spacer plate and two permanently affixed gaskets (1), Figure 5. The spacer plate is designed to route fluid to apply the overrun clutch in the gears.
While towing a trailer equipped with electric brakes and if the trailer brakes are applied manually and the vehicle speed drops below 21 km/h (13 mph), the vehicle may go into auto start/stop mode even if the vehicle's brake pedal is not being depressed. The trailer brake operation will still work.
If the vehicle will not be in use for a period of 30 days or more, disconnect the 42 volt battery power from the vehicle in order to prevent the batteries from discharging. The battery disconnect switch is located on the passenger side of the energy storage box.
After an airbag inflates or there is a right side impact, the automatic battery cut-off switch will open and the 42 volt battery will be disconnected. The 42 volt electrical power to the vehicle will be off and the vehicle will not start. The automatic battery disconnect must be reconnected by a qualified service technician.
When cold, the customer may notice that the engine shuts off at the first stop, but then does not shut off again until the engine/vehicle is warm. At the first stop, the batteries have been discharged. Because the batteries are cold, the batteries are slow to recharge, which will prevent the vehicle from going into "Auto-Stop" mode. Auto-Stop mode will resume when the vehicle is warm and the batteries are recharged.
Battery voltage will fluctuate during deceleration. When the 42V system is fully charged, the energy created during regenerative braking is used to recharge the 12V battery. During this process, the customer may notice a fluctuation on the voltage gauge.
A low oil pressure warning will display on the DIC during the transition from the APO continuous mode to vehicle run or a quick key off-on cycle. The low oil pressure message is displayed by the PCM because the PCM never went to sleep/shut down during these events. Because the PCM didn't shut down, the PCM thinks the vehicle has stalled, therefore displaying the low oil pressure message. This message will disappear as soon as the key is cycled off.
The airbag disable switch backlight flickers. This is caused by a small fluctuation of current through the circuit.
At 32 km/h (20 mph) the fan is programmed to turn on. The fan is programmed to shut off at 24 km/h (15 mph) or below. During a fast deceleration, it is possible to still hear the fan at very low speed.
From the driver's seat, this sound may appear to be coming from the transmission/electric machine area. From the passenger seat, the sound will appear to be coming from the front of vehicle/A-pillar area. This noise is normal and is caused by the system charging.
The following information may be helpful in diagnosing customer concerns:
U1883 & U1884 communication fault codes between the HCM & DDM/PDM occur undetected by the customer. They do not set MIL warnings. They are only induced by electrical backfeed of the towing harness ground circuit when electric towing brakes are activated. Even though this ground backfeed induces class2 bus noise through the DDM & PDM modules, no functional impact to the vehicle results.
Repair:
Clear codes U1883 & U1884.
There are two transmission Diagnostic Trouble Codes (DTCs) that are used for Transmission Secondary Fluid Pump - DTC P2796, Auxiliary Transmission Fluid Pump Relay Control Circuit and DTC P2797, Auxiliary Transmission Fluid Pump Performance.
DTC P2796 will detect a continuous open circuit, a short to ground or a short to power in the Auxiliary Transmission pump circuit. DTC P2797 will detect a TFP Switch signal C (D4) state change while in the engine idle off mode. Both DTCs are monitored by the Hybrid Control Module (HCM).
Scan tool interface is thru the SGCM. The pump can be turned on by operating the Aux. Pump Relay ON and OFF. This is located in the Special Functions Output Controls on the scan tool. Refer to the current service manual for the diagnostic information.
Important: The secondary fluid pump assembly is not repairable. If the pump needs repair, the unit is replaced. The pump has a replaceable filter element, however it does not require regular maintenance.
The brake pedal position sensor calibration must be performed after the brake pedal position sensor or the electro-hydraulic power steering (EHPS) system has been serviced. The calibration procedure will set the brake pedal position sensor home value. This value is used by the EHPS to determine the brake pedal position and the brake pedal rate. Refer to SI Document ID #1367196.
A service brake system message will appear on the DIC anytime the vehicle's wheels are driven but no input is received from the hand/wheel speed sensor. This would typically be encountered while working with the vehicle on a hoist. DTC C0544 will also be stored in history. When this occurs, clear the code and no further action is required.
Inside the SGCM is a fluid called Floranert that cools the electronics along with the external cooling system. Never attempt to remove the coolant pressure relief valve. Doing so will damage the SGCM capabilities to perform and will require a new unit.
There is a coolant pressure relief valve on the SGCM. Refer to the diagram above. It is important NOT to remove this screw. If the screw is removed, the SGCM will have to be replaced. Note: SGCM's are expensive and could be charged back due to negligence.
Jump starting a hybrid vehicle may take considerably longer than a regular vehicle. It may take 10-20 minutes for a hybrid vehicle to charge from another vehicle's 12 volt battery in order to start a hybrid vehicle. Jump start mode is only entered if the engine fails to crank. The jump start mode will continue up to 20 minutes and will terminate automatically. The jump starting procedure may be able to be repeated if the engine fails to crank. If the vehicle cranks but fails to start, this will not cause the vehicle to go into jump start mode.
A replacement battery (Panasonic) for the battery pack is delivered with an 80% SOC (state of charge). It is necessary to charge the battery to 100% SOC using a battery charger, prior to installation. One option to charge the vehicle is to use the Battery pack service charge procedure (see below).
Important: A special battery charger (J 42634 -- Battery Module Charger) is required to charge the batteries located in the ESB (Energy Storage Box).
A battery pack service charge is performed using the Tech 2, a battery charger and the SGCM/ESCM. To initiate a service charge using the Tech 2®, go into SGCM special functions. It is necessary to perform a battery pack service charge if one or more of the batteries are diagnosed with a low charge or a battery fault and must be performed BEFORE battery replacement.
A Battery Pack Service Charge Procedure (refer to SI document ID #1462080) MUST be performed at the pack level if one of the following apply:
Important: • If the battery charger is turned off, or disconnected during the battery pack service charge procedure, the battery pack may discharge to an unacceptable State-of-Charge. If this event occurs, be certain to terminate the battery pack service charge procedure. • Once the key is turned off, do not turn the key back on once the service charge is initiated or it will terminate the service charge prematurely.
The PCM will store all the codes for the ESCM, EHPS, HCM and SGCM. This doesn't mean a PCM failure. The other modules do not store codes but rather transmit their codes to the PCM where the codes are stored. Diagnose the appropriate component/module based on the code found in the PCM.
If updating/replacing one module, verify that all the other modules are also updated.
Important: • The Panasonic batteries are designed to have a life span of approximately 36,000 amp hours. Amp hours should not be used for diagnosis or determine when to replace the batteries. The actual battery health should be determined using the appropriate battery tester. • If all three batteries are replaced, the total Ahrs must be reset to 0 Ahrs with a scan tool, through BECM Output Controls. Refer to SI Document ID #1372154.
The following list of tools are essential for servicing the Hybrid Truck. In the U.S., these tools have been shipped to Chevrolet and GMC Tier 1 dealers ONLY. In Canada, these tools are shipped to dealers enrolled in the Hybrid Truck program ONLY. An essential tool package is available by calling 1-800-GMTools.
Tool #
Description
J-41479-2A
Seal Holder Assembly
EL-48045*
EHPS Fuse Crimp Tool
EL-42000-30
Terminal Adapters
J-42634
AGM Battery Charger
J-43679-A
Battery Lift Hooks
J-46093
Stator Holding Tool
J-46143
Surge Tank Adapter
*Tool shipped to dealers after 12-1-2005.
The following fluids/lubricants are unique for the HP2. For all other recommended fluids and lubricants, see "Recommended Fluids and Lubricants" in the Owner's Manual.
Usage
Fluid/Lubricant
Power Steering System
Electrohydraulic Power Steering Fluid (GM P/N US 88901975 / Canada 88901976)
Starter/Generator Control Module (SGCM) Engine Coolant
50/50 mixture of clean, drinkable water and use only DEX-COOL® Coolant.
Important: GMLAN application requires Tech 2® and CANDi module to view and control functions.
The Hybrid truck will have two methods of communication among the modules - class2 and GMLAN. Only the modules related to the hybrid option communicate via the GMLAN. The PCM records all DTCs related to the hybrid control modules.
Important: • When updating any module on Class2, it is necessary to disconnect the electro-hydraulic power steering pump. During programming the electro-hydraulic power steering pump runs continuously. If this occurs, hybrid modules will need to be replaced. • When updating any module on the GMLAN, U-codes will set and must be cleared.
Performing a quality pre-delivery inspection is one of the most important functions your dealership can do for the customer. Most customers consider the condition of their new vehicle during delivery as a direct reflection of your dealership and your service department. A quality PDI is essential to improving a customer's perception of your dealership and increasing his/her satisfaction with their new vehicle.
Important: The following two items should be noted in addition to performing the normal PDI procedure.
When the engine is warm, it is important to purge any air that is in the system. Failure to do so can cause the starter/generator to overheat. The following steps should be followed to purge the system:
If the vehicle will not be in use for a period of 30 days, disconnect the 42 volt battery power from the vehicle in order to prevent the batteries from discharging. The battery disconnect switch is located on the passenger side of the energy storage box.
Two new labor operations have been established for service of the Secondary Fluid Pump.
K6541 - Pump Assembly, Secondary Fluid - Replace
K6542 - Filter Assembly, Secondary Fluid - Replace
