[52B] SUPPLEMENTAL RESTRAINT SYSTEM (SRS) - - SYSTEM OPERATION - SRS-ECUPRINT PAGE / INDEX / PRIOR / NEXT
SRS-ECU
The SRS-ECU incorporates an analogue G sensor and safing G sensor for frontal collisions.
In frontal collisions, the driver's and front passenger's air bags deploy only when both the analogue and safing G sensors detect simultaneously a collision-induced G of a level exceeding the threshold as in the case with the conventional system.
The SRS-ECU incorporates the impact detection door unlock signal process circuit.
The SRS-ECU is provided with the following capabilities:
  • Backup power supply in case of power failure in collisions: Back up capacitor
  • Boosting function in case of battery voltage drop: DC - DC converter
  • Self-diagnosis function to avoid system's operation errors and improve its reliability
 CAUTION
 Never disassemble the SRS-ECU.
DIAGNOSIS FUNCTION
The SRS-ECU has the following functions to make system checking using MUT-II/III easy.
  • Diagnosis code output
  • Service data output
DIAGNOSIS CODE OUTPUT
The SRS-ECU diagnoses the following items and stores a diagnosis code in the non-volatile memory (EEPROM*1) when a problem is detected.
Therefore, the memory is not deleted after a battery terminal is disconnected. (The diagnosis code memory can be deleted by the MUT-II/III.)
CODE NO.
 MAJOR CONTENTS OF DIAGNOSTICS
1A*4
Front impact sensor LH system
 Short circuit in the sensor
1B*4
Open circuit in the sensor
1C*4
Short circuit in the power supply
1D*4
Short circuit in the earth
2A*4
Front impact sensor RH system
 Short circuit in the sensor
2B*4
Open circuit in the sensor
2C*4
Short circuit in the power supply
2D*4
Short circuit in the earth
11*5
Front impact sensor short-circuited
12*5
One front impact sensor open-circuited
13*5
Two front impact sensor open-circuited
14
 Analogue G-sensor malfunction
15
 Safing G-sensor short-circuited (for frontal collision)
16
 Safing G-sensor open-circuited (for frontal collision)
17
 Safing G-sensor malfunction (for side collision)
21*3
Driver's air bag squib short-circuited
22*3
Driver's air bag squib open-circuited
24*3
Passenger's (front) air bag squib short-circuited
25*3
Passenger's (front) air bag squib open-circuited
26*3
Driver's pre-tensioner squib short-circuited
27*3
Driver's pre-tensioner squib open-circuited
28*3
Passenger's (front) pre-tensioner squib short-circuited
29*3
Passenger's (front) pre-tensioner squib open-circuited
31
 SRS-ECU capacitor circuit voltage too high
32
 SRS-ECU capacitor circuit voltage too low
34*2
SRS-ECU connector lock out of order
35
 Ignition of the air bag completed
39*4
Simultaneous deployed
41*2
Power supply voltage (IG1 (A) voltage) drops abnormally.
42*2
Power supply voltage (IG1 (B) voltage) drops abnormally.
43*2
SRS warning lamp circuit open-circuited
44*2
SRS warning lamp circuit malfunction
45
 SRS-ECU non-volatile memory (EEPROM*1 ) and A/D converter system
46*2 *4
Faulty installation
51
 Driver's air bag squib activating circuit short-circuited
52
 Driver's air bag squib activating circuit open-circuited
54
 Passenger's (front) air bag squib activating circuit short-circuited
55
 Passenger's (front) air bag squib activating circuit open-circuited
56
 Driver’s seat belt pre-tensioner (squib ignition drive circuit) system detected short
57
 Driver’s seat belt pre-tensioner (squib ignition drive circuit) system detected open
58
 Passenger’s seat belt pre-tensioner (squib ignition drive circuit) system detected short
59
 Passenger’s seat belt pre-tensioner (squib ignition drive circuit) system detected open
61
 Driver's air bag squib drive circuit (power supply side) short-circuited
62
 Driver's air bag squib drive circuit (earth side) short-circuited
64
 Passenger's (front) air bag squib drive circuit (power supply side) short-circuited
65
 Passenger's (front) air bag squib drive circuit (earth side) short-circuited
66
 Driver's pre-tensioner squib (power supply side) short-circuited
67
 Driver's pre-tensioner squib (earth side) short-circuited
68
 Passenger's (front) pre-tensioner squib drive circuit (power supply side) short-circuited
69
 Passenger's (front) pre-tensioner squib drive circuit (earth side) short-circuited
71*3 *5
Side air bag squib (RH) short-circuited
72*3 *5
Side air bag squib (RH) open-circuited
73*5
Side air bag squib (RH) drive circuit shorted
74*5
Side air bag squib (RH) drive circuit open
75*5
Side air bag squib (RH) drive circuit (power supply side) shorted
76*5
Side air bag squib (RH) drive circuit (earth side) shorted
79*5
Side impact sensor (LH) communication error
81*3 *5
Side air bag squib (LH) shot-circuited
82*3 *5
Side air bag squib (LH) open-circuited
83*5
Side air bag squib (LH) drive circuit shorted
84*5
Side air bag squib (LH) drive circuit open
85*5
Side air bag squib (LH) drive circuit (power supply side) shorted
86*5
Side air bag squib (LH) drive circuit (earth side) shorted
89*5
Side impact sensor (RH) communication error
91*2 *5
Side impact sensor (LH) voltage error
92*5
G-sensor of side impact sensor (LH) failure
93*5
Side impact sensor (LH) communication impossible
94*2 *5
Side impact sensor (RH) voltage error
95*5
G-sensor of side impact sensor (RH) failure
96*5
Side impact sensor (RH) communication impossible

NOTE: 
  • *1: Electrically Erasable Programmable ROM
  • *2: This diagnosis code memory will be automatically cleared from the memory and the SRS warning lamp will be switched off when the system returns to normal condition.
  • *3: The diagnosis codes will remain in memory and the SRS warning lamp will be switched off if the system returns to normal condition.
  • *4: Vehicles without side air bag
  • *5: Vehicles with side air bag
SERVICE DATA OUTPUT
When the SRS-ECU detects a problem, it stores a diagnosis code and the duration that the problem has lasted in the non-volatile memory. In addition, how often a diagnosis code and duration are cleared by the MUT-II/III are stored in the non-volatile memory as a reference for service work. This data can be read by the MUT-II/III.
No.
 Service Data Item
 Applicability
92
 Number indicating how often the memory is cleared
 Maximum time to be stored: 250 days
93
 How long a problem has lasted (How long takes from the occurrence of the problem until the first air bag squid Igniting signal)
 Maximum time to be stored: 9999 minutes (approximately 7days)
94
 How long a problem has lasted (How long from the first air bag squib igniting signal until now)

[52B] SUPPLEMENTAL RESTRAINT SYSTEM (SRS) - - SYSTEM OPERATION - SRS-ECUPRINT PAGE / INDEX / PRIOR / NEXT
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