Specifications

Figure 5. Typical OBD to RS232 Interface
+5V
3.58MHz
27pF
4.7KΩ
+5V
2.2KΩ
78L05
+5V
0.01µF
‘Power On’
LED
15
(L Line)
7
(K Line)
5
(Signal
Ground)
16
(Battery
Positive)
OBD
Interface
Notes: -
-
-
NPN transistors are
2N3904 or similar
PNP transistors are
2N3906 or similar
Diodes are 1N4148,
1N4001, etc.
10KΩ
1
2
3
4
7
6
5
323
14
13
12
11
8
9
10
27pF
510Ω
10KΩ
2.2KΩ
510Ω
330Ω330Ω
+5V +5V
750Ω
0.1µF
Status
LEDs
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ELM323
2 (RxD)
5 (SG)
3 (TxD)
47KΩ
100KΩ
0.1µF
RS232
Interface
(DB9F)
4.7KΩ
10KΩ
+5V
1 (DCD)
4 (DTR)
6 (DSR)
7 (RTS)
8 (CTS)