ACC Electronic Control Module - Installation

Category:
Body

Section:
8

Page:
99

Issue:
01/95-0537

Code:
870

Subject:
ACC Electronic control Module

Application: 1990-93 9000 Models with ACC 2

Supersedes PSI 01194-0429

A new ACC ECM was introduced in early M94 production as of VIN Serial No. R1006299. This new and improved ECM incorporates software which eliminates the risk of false diagnostic trouble codes being generated for rear AC. The software changes also make the system more user friendly. This ECM may be installed on an earlier car where there is a customer complaint that cannot be rectified by other means.




When a 1994 ACC ECM (see part number below) is fitted in M9093 cars, all jumper connections and resistors that may have been added in previous repairs in the wiring harness must be removed. See Figure 1.

CARS AFFECTED:

1990-1993 9000 Models with ACC 2

PARTS:

ACC Electronic Control Module 88 28 709

ACTION:

1. Unplug the 39pin and 124pin connectors at the rear of the ACC ECM.

2. Remove the jumper connection, if any. between pins 30 and 32 on the 39pin connector. Insulate the lead.

3. M1990-1991

Snip or remove the lead to pin 32. Insulate the lead.

4. Remove the resistor, if any, between lead 623 (black) in the 12-pin connector and lead 407 (yellow/white) in the 3 pin connector. Insulate the lead.

5. Fit the new ACC ECM and calibrate it.


FALSE DIAGNOSTIC TROUBLE CODES (DTC) ENCOUNTERED WITH ACC 2:

Certain trouble codes may be encountered with ACC 2 even if no such fault exists. The diagnostic trouble codes concerned are shown below:

D6891/E6891 Sun sensor, no pulses
26391 Break, ambient temperature signal
33421/53421 Solenoid valve for rear AC, break
33672/53672 Fan, interior temperature sensor, shorting to ground

*Eliminated with M94 ACC ECM, P/N 88 28 709


ACTION:

Should any of the above diagnostic trouble codes occur:

1. Clear the codes by means of the ISAT.

2. Start the engine and check whether the trouble codes are generated again.

If the trouble code does not reappear, no further action will be necessary

3. If the diagnostic trouble codes are newly generated. trace the fault using Service Manual 8:3 Automatic climate control ACC II.

WARRANTY INFORMATION:

For warranty repairs based on a customer complaint, please use Failure Coding 87080-67-0-01-01. Labor allowance is Operation No. 87080 (0.2 hour). Add 0.1 hour in straight time for the above modifications. Add Operation No. 12807 (0.3 hour) for ACC-ISAT Diagnostic Time.