What does the diagnostic unit look like on a 1995 Volvo 850? Where is it found?

Answer 1

if your talking about the diagnostic check connector, they are under the hood on the left side by the radiator core support and behind the headlight area. there are 2 of them

With Automatic Transmission
Notes

GENERAL DESCRIPTION
The ECM's on-board diagnostic capabilities can be accessed through the diagnostic socket. The diagnostic socket has three Diagnostic Test Modes (DTM ) as explained below.

Diagnostic Test Mode 1 (fault codes):
The on-board diagnostic system carries out continuous system checks and monitors several components during engine operation. If the ECU detects a problem in a system or component, it stores a fault code in its memory.

Diagnostic Test Mode 2 (input device test):
Diagnostic Test Mode 2 aids the technician in checking the operation of selected ECM input devices. An acknowledgement code tells the technician if the input device is operating correctly or not.

Diagnostic Test Mode 3 (output device test):
Diagnostic Test Mode 3 aids the technician in checking the operation of selected ECU output devices. By placing your hand on the component or listening for component operation sounds, you can verify if the output device is operating.

Diagnostic Connectors



Diagnostic Socket Operation :
The diagnostic socket has a button, a light diode and a selector cable. When carrying out fault tracing, the selector cable must be placed in its appropriate socket.

* For engine management trouble shooting use SOCKET #2 (of the 6) on DLC "A" .

Checking For More Codes



Diagnostic Test Mode 1 (fault codes): is activated by a single brief operation of the test button. The ECM responds by displaying any stored DTC's.

NOTE: After reading of the DTC's the ignition must be switched OFF before the engine is STARTED, or else the Malfunction Indicator Lamp (MIL ) will light up irrespective of whether there are any codes or not, until engine speed exceeds 2000 rpm.

Entering Control Function #2



Diagnostic Test Mode 2 (input device test): is activated by two brief operations of the test button, causing the LED to flash rapidly. The ECM will then deliver acknowledgement codes. See INPUT DEVICE TEST for more information.

Entering Control Function #3



Diagnostic Test Mode 3 (output device test): is activated by three brief operations of the test button. The ECM responds by operating several components in order. See OUTPUT DEVICE TEST for more information.

Code Example



Codes stored in the memory are displayed by a series of flashes from the light diode in the diagnostic socket. All codes have three numbers, each ranging from 1-9. The code is read by the number of flashes delivered by the diode.

Since all codes have three numbers, each code requires three series of uninterrupted flashes. There is a three second interval between the series of flashes to make the codes easy to read.