How to read the circuit diagram of automobile combination instrument system

Taking the circuit diagram of the instrument cluster of the Volkswagen Bora series as an example, we will introduce the method of reading the circuit diagram.

1. Reading the power supply circuit of the combination instrument

Combined instrument system circuit diagram—power supply circuit

① Battery positive electrode → SA3, 110A → SC13, 5A → Internal connecting wire A167 → T32/4 of instrument control unit J285.

② Ignition switch 15 → SC2, 10A → internal connecting wire A20 → T32/23 of instrument control unit J285.

③ Oil pump circuit. From fuel pump relay J17 terminal 87 → SC45, 15A → address code 55 → fuel pump G6 → ground.

④ High beam circuit. Manual dimmer switch E4 (i.e. overtaking light switch, toggle switch, the power of the light switch passes through the manual dimmer switch contact to the manual dimmer switch T12/12 pin) → SC18, 15A → Internal connection line A95, divided into three road:

First path: left high beam bulb M30.

Second path: Right high beam bulb M31.

The third path: T32/25 of the instrument control unit J285 (to control the instrument high beam indicator K1 to light up).

2. Read the circuit diagram of the turn indicator light, parking brake indicator light, and multi-function display

Instrument panel circuit diagram—turn indicator light, parking brake indicator light, multi-function display

E22—intermittent window wiper switch; E38—window wiper intermittent operation regulator; E86—multifunction display call button; E92—reset button; F9—hand brake control switch; J119—multifunction display ;J285—control unit in the instrument panel; J519—body control module, under the left side of the instrument panel; K65—left turn signal indicator; K94—right turn signal indicator; T2y—2-core black plug connection; T6c— 6-pin black plug connection; T8d-8-pin black plug connection; T32-32-pin black plug connection; T73a-73 white plug connection; 44-ground point, under the left A-pillar; 45-ground point, in the middle of the instrument panel On the right bracket of the air conditioner; 371—Ground connection 6 in the main harness; 373—Ground connection 8 in the main harness; 374—Ground connection 9 in the main harness; 605—Ground point, on the upper part of the steering column

K65 and K94 are left and right turn indicators. The body computer J519 receives the switch signal of the turn switch or hazard warning light or anti-theft remote control and transmits the signal to the instrument computer through the CAN line. The instrument computer then controls the indicator light to light up; instrument plug Pin T32/6 is the instrument ground.

T32/12 is the parking brake signal input and controls the parking brake indicator light. When the parking brake handle is pulled up, the parking brake indicator light lights up, and when it is lowered, the parking brake indicator light goes out.

E38 is on the wiper lever. It changes the resistance value by adjusting the regulator switch and sends a signal to the body computer J519. J519 controls the intermittent time of the wiper motor. E92 and E86 switches are also on the wiper lever and can adjust the instrument panel. The display mode of the LCD monitor switches between instantaneous fuel consumption, average fuel consumption and other display interfaces.

3. Read the circuit diagram of the coolant temperature gauge and fuel inventory display gauge

Instrument system circuit diagram—coolant temperature gauge, fuel inventory display gauge

G—Fuel stock display sensor; G1—Fuel stock display; G3—Coolant temperature gauge; G6—Fuel pump; G17—Outdoor temperature sensor; G32—Low coolant display sensor; J285—Control unit in instrument panel; J519— Body control module, under the left side of the instrument panel; K28 - indicator light for coolant temperature and coolant low display; K105 - fuel reserve indicator light; K169 - gear selector lock indicator light; T2g - 2-pin black plug connection; T2s — 2-core black plug connection; T5a — 5-core black plug connection; T32 — 32-core blue plug connection; 45 — ground point, on the right bracket of the air conditioner in the middle of the instrument panel; 269 — ground connection in the instrument panel wiring harness ( Sensor Ground) 1; 370—Ground connection 5 in the main harness; 372—Ground connection 7 in the main harness

The instrument connector terminal T32/5 is the universal instrument computer ground for the sensor; G17 is the outside temperature sensor, which detects the outside temperature. The instrument computer receives this signal and controls the multi-function display to display the outside temperature value.

G32 is the coolant level sensor, which is used to detect whether the coolant is sufficient. When the coolant is insufficient, the indicator light K28 for the coolant temperature and coolant insufficient display on the instrument will be lit. The coolant temperature gauge G3 is controlled by the engine water temperature sensor G52. G52 transmits the signal to the engine computer. The engine computer sends the signal to the instrument computer through CAN to control G3. When the water temperature is too high, the K28 indicator light will also light up.

The fuel storage level display sensor G is used to detect the fuel level in the fuel tank and control the fuel level display G1; when the fuel level is insufficient, it will remind the driver to refuel as soon as possible. The reminder will not only be through the display but also through an alarm sound.

4. Rear fog light indicator and brake pad wear indicator circuit diagram reading

Instrument system circuit diagram—rear fog light indicator, brake pad wear indicator

E18—rear fog light switch; F34—brake fluid level warning signal contact; G34—left front brake pad wear sensor, in the left front wheel; J285—control unit in the instrument panel; J519—body control module, in the instrument panel Under the left side of the plate; K13—rear fog light indicator; K31—GRA indicator; K32—brake friction plate indicator; K47—ABS indicator; K75—airbag indicator; K83—exhaust warning light; K118 — Braking system indicator light; L46 — Left rear fog light bulb; T2u — 2-core black plug connection; T2v — 2-core black plug connection; T3h — 3-core black plug connection; T17 — 17-core black plug connection; T32 — 32-pin blue plug connection; 179—Ground connection in the left headlight harness; 366—Ground connection 1 in the main harness; 379—Ground connection 14 in the main harness; 640—Ground point, in the middle of the top of the left front longitudinal beam; A88—Connection in the instrument panel wiring harness (NSL); B268—Connection 1 in the interior wiring harness (brake pad wear display); *—Only cars equipped with brake pad wear alarm

E18 is the rear fog light switch. When the rear fog light switch is turned on, T17/9 of E18 is powered → left rear fog light bulb L46 → grounded → T32/1 of the instrument computer J285 (to control the rear fog light indicator K13 point Bright).

G34 is the left front brake pad wear sensor, which is installed in the left front brake pad. When the brake pad wears to the replacement limit, the instrument brake pad indicator K32 will light up to remind the driver to replace the brake pad.

F34 is the brake fluid level warning signal contact, used to detect whether the brake fluid is sufficient. When the brake fluid is insufficient, the brake fluid level is too low, the F34 contact is closed, and the brake system indicator K118 lights up to remind the driver. Check the brake system and replenish brake fluid.

5. Reading engine tachometer and speedometer circuit diagrams

Instrument system circuit diagram—engine tachometer, speedometer circuit diagram

G5—Engine tachometer; G21—Speedometer; H3—Buzzer and alarm sound; J285—Control unit in the instrument panel; J519—Body control module, under the left side of the instrument panel; K2—Alternator indicator light; K19— Seat belt alarm indicator light; K48—shift display indicator light; K132—electronic throttle failure signal light; K155—ASR indicator light; K166—door open indicator light

The tachometer G5 displays the engine speed. The engine speed sensor detects the engine speed and sends the signal to the engine computer. The engine computer transmits the signal to the instrument through the CAN line and then controls the tachometer G5 to display the engine speed.

There are many other warning lights in the instrument, each of which is controlled by corresponding switches and sensors transmitting corresponding signals through the CAN bus. Their main function is to enable the driver to better understand the vehicle status.

6. Reading the oil pressure gauge switch circuit diagram

The oil pressure switch F1 is a pressure switch used to detect the engine oil pressure. When the engine oil pressure is insufficient, the oil pressure indicator K3 lights up.

Instrument system circuit diagram—oil pressure switch circuit diagram

F1 - oil pressure switch; J245 - sliding sunroof control unit; J285 - control unit in the instrument panel; J519 - body control module, under the left side of the instrument panel; K3 - oil pressure indicator light; R - radio; T1g - 1 core black Plug connection; T6e - 6-pin black plug connection; T8c - 8-pin black plug connection; T14a - 14-pin black plug connection, behind the left headlight in the engine compartment; T32 - 32-pin blue plug connection; T73a - 73-pin white plug Plug connection; B383 - connection 1 in the main wiring harness (drive system CAN bus high frequency); B390 - connection 1 in the main wiring harness (drive system CAN bus low frequency); B476 - connection 12 in the main wiring harness; * - equipment only Cars without navigation systems