2.5L Engine, Updated EPROMS - O2 Sensor Malfunction (12 05 93 (3916))

Publication date: 1994-01-01
Reference number: 12 05 93 (3916)

2.5L ENGINE, UPDATED EPROMS - O2 SENSOR MALFUNCTION

TECHNICAL SERVICE BULLETIN

Reference Number(s): 12 05 93 (3916)

UPDATED EPROMs FOR VEHICLES WITH M50 ENGINE

Model(s): 1989-92 BMW 525i

1992 BMW 325i

Group: 12 - Engine Electrical

Bulletin No.: 12 05 93 (3916)

Date: January, 1994

SUBJECT

Updated EPROMs For Vehicles With M50 Engine

COMPLAINT

CHECK ENGINE Light On - Oxygen Sensor

CAUSE

Malfunction of the oxygen sensor is possibly due to "thermal shock". Thermal shock may occur only under certain environmental conditions when a cold engine is started and moisture/condensation in the exhaust passes over the heated oxygen sensor causing a rapid cooling of the sensor's outer ceramic shell. This rapid cooling may cause the ceramic shell to shatter or crack.

The previous update for this complaint introduced a delay to the activation of the oxygen sensor heater relay based upon engine temperature. While this has proven to be quite successful, we are still seeing a small number of cases of oxygen sensor failure due to thermal shock. This is due to the fact that the exhaust system cools down much more rapidly than the engine block, causing an insufficient delay before activating the heater relay in cases of a restart on a warm engine. This latest update includes the previous delay based upon engine temperature, and will also evaluate the engine load when determining the proper time to switch on the heater relay.

CORRECTION

VEHICLES PRODUCED THROUGH MODEL YEAR "92" (NON-VANOS)

A Service Action is forthcoming on these vehicles which will involve the replacement of the engine control module EPROM. In the event of an oxygen sensor failure, update the engine control module EPROM if it is not of the latest BMW Hardware Number. Please refer to the Parts Information section of this bulletin for the applicable part numbers. Latest control modules have BMW Hardware Number 1 740 352, 174 353, or 1 740 354.

REPAIR PROCEDURE

Please refer to the ENGINE CONTROL MODULE EPROM REPLACEMENT section in this article for complete instructions on the replacement of the EPROM in the engine control module.

PARTS INFORMATION

Control Modules With Bosch Hardware Number	Model	Transmission	Order EPROM Part Number
0 261 200 403	E34, E36	Manual	01 00 1 468 573
0 261 200 403	E34, E36	Automatic	01 00 1 468 574
0 261 200 402	E36	Manual	01 00 1 468 575
0 261 200 402	E36	Automatic	01 00 1 468 576
0 261 200 402	E34	Manual	01 00 1 468 579
0 261 200 402	E34	Automatic	01 00 1 468 580
0 261 200 402	E34 Touring	Automatic	01 00 1 468 617
0 261 200 405	E34, E36	Manual	01 00 1 468 577
0 261 200 405	E34, E36	Automatic	01 00 1 468 578

SERVICE ACTION LABEL INSTRUCTIONS

The repair described in this Service Information bulletin is not a Service Action at this time and is only to be performed on vehicles in the event of and oxygen sensor failure. On vehicles WITHOUT VANOS (produced through "92 Model Year), a Service Action will be announced shortly. For future identification of vehicles which have received this repair, after performing the repair obtain a label (SD 92-031) and:

A.) Emboss your BMW dealer warranty number in the middle of the label (1);

B.) Punch out code number 105 printed on the label (2); and

C.) Bend label to crease an edge and remove the backing paper. Then affix it to the "B" pillar as shown in Fig 1 .

Fig 1: Service Action Label Installation

If the car already has a label from a previous Service Action/Recall Campaign, affix this label next to the old one. Do not affix one label on top of another because a new number from an underlying label could appear in the punched out hole of the new label.

ENGINE CONTROL MODULE EPROM REPLACEMENT

REPAIR PREPARATORY INSTRUCTIONS

The installation of the updated EPROM into the engine control module is a simple procedure. However, before beginning the EPROM exchange, the following conditions must be provided and the designated tools must be used.

ENVIRONMENT

The work area where the EPROM is exchanged must be free of excessive dust and aggressive chemicals or vapors. A small uncarpeted office within the dealership is recommended. Since low atmospheric humidity promotes static electricity, an evaporating bowl of water can be used to raise the humidity level of the work area.

EQUIPMENT

Screwdrivers (blade type) are only used to open and close the engine control module. The EPROM is exchanged using an IC extractor/inserter set. Tool sets can be obtained locally (Radio Shack, Archer #276-1581).

STATIC ELECTRICITY

The engine control module can be damaged and rendered unusable by static electrical discharge. For this reason the 3M static protection kit (or equivalent) must be used during the entire EPROM exchange procedure. See S.I. 04 30 87 (1546) for complete details.

EPROM STORAGE

Replacement EPROMs must be stored in the original shipment containers. The label in the center of the EPROM must never be removed

REPAIR PROCEDURE

CAUTION: Whenever connecting or disconnecting any control module the IGNITION MUST BE SWITCHED OFF

Remove the four (4) screws (Torx T20) from the topside of the control module. See Fig 2 .

Fig 2: Control Module Cover Retaining Screw Locations
Lay the control module face down on the static mat and carefully bend up the six (6) tabs only as far as necessary to remove the cover. See Fig 3 . On M3.1 control modules, remove the retaining pin from the plastic rivet using needle nose pliers. See Fig 4 .

Fig 3: Bending Control Module Cover Tab

Fig 4: Removing Plastic Rivet Retaining Pin
Remove the cover from the control module.
On control modules with an upper circuit board, remove the white plastic cover from the top side of the control module.
On control modules with an upper circuit board, carefully separate the two circuit board support towers. See Fig 5 . Gently raise the rear of the upper circuit board and fold the connecting ribbon out between the two circuit boards.

Fig 5: Separating Circuit Boards
On control modules with an upper circuit board, while gently raising the back of the upper circuit board, release the two front retaining clips in the connector plug. See Fig 6 .

Fig 6: Releasing Connector Plug Retaining Clips
On control modules with an upper circuit board, slide the circuit board backwards out of the connector and rotate upwards. See Fig 7 . Lay the open control module out on the static mat.
NOTE: This procedure is easiest to perform if the back of the circuit board is raised and a slight downward pressure is exerted on the connector pins of the upper circuit board.

Fig 7: Opening Control Module
Remove the EPROM security cap (1) by inserting a small straight blade screwdriver into the slot on each long side and releasing the catch by gently prying outward against the side. See Fig 8 and Fig 9 .

Fig 8: EPROM Security Cap Location

Fig 9: Removing EPROM Security Cap
Remove the EPROM from the circuit board using the IC extractor tool. See Fig 10 .

Fig 10: Removing EPROM From Circuit Board

CAUTION: Do not touch the contact pins of the EPROM.
Install the new updated EPROM using the IC inserter tool (1). See Fig 11 .

Fig 11: Installing EPROM

NOTE: The EPROM is correctly installed when the notch in the EPROM aligns with the notch in the IC socket (2). Assure that all the EPROM contact pins are fully inserted by pushing down on the EPROM until the stop is felt.
Reinstall EPROM security cap.
On control modules with an upper circuit board, reinstall upper circuit board and place white plastic cover on top.
Reinstall cover with four (4) Torx screws and bend tabs down.
Affix "BMW NA Quality Control" label (P/N 01 00 1 467 895) on the front of control module for future identification of modification to control module. One label will be included with each EPROM ordered.