Montero V6-3.8L SOHC (2005)
Hydraulic Brake Booster: Testing and Inspection
Description of On-Board Diagnostics
INTRODUCTION
The hydraulic brake booster (HBB) accumulates the high-pressure brake fluid in the accumulator by operating the pump motor. Even though the
working sound of the pump motor can be heard during operation, this sound is usually generated at normal operation of the HBB and is not an
indication of a malfunction.
HBB Diagnostic Trouble Code Detection Conditions
HBB diagnostic trouble codes (HBB DTCs) are set under different conditions, depending on the malfunction detected. Most HBB DTCs will only be
set during vehicle operation. Some HBB DTCs will also be set during the HBB self-check immediately after the engine is started.
After erasing an HBB DTC, duplicate the HBB DTC set conditions to see if it resets. Depending on the detection timing and set conditions for the
specific HBB DTC, you must either drive the vehicle or turn the engine off and restart it. To set the proper conditions for that DTC again, refer to
"HBB DTC SET CONDITIONS" for each HBB DTC that you are trying to reset.
Diagnostic Strategies
DIAGNOSTIC TROUBLESHOOTING STRATEGY
Use these steps to plan your diagnostic strategy. If you follow them carefully, you will be sure that you have exhausted most of the possible ways to
find an HBB fault.
1. Gather information about the problem from the customer.
2. Verify that the condition described by the customer exists.
3. Check the vehicle for any HBB DTC.
4. If you cannot verify the condition and no HBB DTC sets, it can be assumed that the malfunction is intermittent. Refer to How to use
Troubleshooting/Inspection Service Points- How to Cope with Intermittent Malfunctions.
5. If you can verify the condition but no HBB DTC sets, or the system cannot communicate with the scan tool, check that the basic brake system is
operating properly.
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If the basic brake system is not operating properly, refer to "Basic Brake System Diagnosis".
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If the basic brake system is operating properly, refer to "Symptom Chart". See: Symptom Related Diagnostic Procedures/Symptom Chart
6. If an HBB DTC sets, record the number of the DTC, then erase the DTC from the memory using the scan tool.
7. Duplicate the HBB DTC set conditions to see if the same HBB DTC will set again.
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If the same HBB DTC sets again, perform the diagnostic procedures for the DTC.
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If you cannot make the same HBB DTC set again, it can be assumed that the malfunction is intermittent. Refer to How to use
Troubleshooting/Inspection Service Points- How to Cope with Intermittent Malfunctions.
Reading Diagnostic Trouble Codes
Retrieving HBB Diagnostic Trouble Codes
Required Special Tools:
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MB991958: Scan Tool (MUT-III Sub Assembly)
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MB991824: Vehicle Communication Interface (V.C.I.)
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MB991827: MUT-III USB Cable
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MB991911: MUT-III Main Harness B
