Faulty Sensor Board Identification; Faulty Pressure-Influence Correction (Faulty Altitude Setting Or Air-Pressure Gauge) - Bosch ETT 008.31 Repair Instructions

8.8 Faulty sensor-board identification
The self-test routine detects faulty equipment on the sensor board.
For "Sensor board" location diagram of components, see section 8.15, "Checking the sensor board".
Check:
- Has the wrong sensor board been installed (check ordering data!)?
- Is there a fault in the hardware?
Using the DMM, measure on the sensor board:
X 83 MA = reference point
UR70 = 2.610 V + 30 m V
Measure U on the sensor board:
REF
UX84 = 5V + 10 m V
If UR70 is faulty, a hardware fault on the motherboard is present or the wrong sensor board has been installed. If, on the other hand,
the voltage is correct, then the connection to the motherboard or the motherboard itself must be defective. Replace these in the specified
sequence. Refer to Sections 10.8 and 10.9.
8.9

Faulty pressure-influence correction (faulty altitude setting or air-pressure gauge)

If the pressure-influence correction in line with the measured values of a built-in air-pressure gauge is switched on, the analyzer
compares the measured value of the air-pressure gauge with the entered altitude. If it finds a measured value which differs from the
mean air pressure - derived from the entered altitude - by > 50 mbar, the device displays an error message.
Possible causes of the fault:
- Incorrectly entered altitude: check according to Section 4.1.7
- Faulty air-pressure gauge or line fault
- Faulty processing of measured values.
Further information about the source of the fault can be called up in test mode as described in Section 4.2. Here, you can read the output
voltage of the air-pressure gauge (in the HC display field) and the displayed value derived from this (mbar, in the engine-speed display
field) during undisturbed operation.
If the air-pressure gauge is faulty, Err 1
gauge continues to be displayed).
Err 1 Err 1
Display Err 1 Err 1 Err 1:
Fine-tuning of the air-pressure gauge was carried out / ended incorrectly. Fine-tune the air-pressure gauge as
described in Section 6.5.
Err 2 Err 2: Err 2
Display Err 2 Err 2
The analyzer detects negative voltage at the input of the air-pressure gauge.
The air-pressure gauge normally keeps its output (ANAK - 1) inside the range 0 V (= 700 mbar) to + 4.7 V
(1100 mbar).
Err 3: Err 3 Err 3
Display Err 3 Err 3
The measured ambient pressure differs from the air pressure derived from the entered altitude by > 50 mbar.
Prüfen: U -1 = OV bis + 4.7 V
ANAK
For test point R74 see function diagram or component location diagram of sensor board in Section 8.15.
Replace the air-pressure gauge or sensor board depending on the results of your tests (refer to Section 10.9).
Err 1, Err 2 Err 1 Err 1 Err 1 Err 2 or Err 3 Err 2 Err 2 Err 2 Err 3 appears in the engine-speed display field (the output voltage of the air-pressure Err 3 Err 3 Err 3
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