Description

BMW L6, M6 1987 Troubleshooting Manual

You have a 1987 BMW L6 or M6 on the lift, and the electrical system is doing something that doesn’t make sense. Maybe the ABS light is on, the self-leveling suspension is dead, or the injection electronics are acting up. Without a factory schematic, you are guessing. Guessing costs you time, blows fuses, and can fry a $400 ECU. I have seen it happen. That is why you need this BMW L6, M6 1987 Troubleshooting Manual — the actual OEM book BMW of North America printed in 1987, not some aftermarket re-draw. 188 pages, factory wire colors, and the same diagnostic flow the dealers used.

Systematic Troubleshooting: The Method Before the Multimeter

Page 4 of this manual explains exactly how to use the schematics. Every switch and sensor is shown at rest — ignition off. The power distribution schematic (section 0670) shows current feed from battery and alternator to every fuse. You combine that with the circuit schematic for a complete picture. Too many guys jump straight to component testing without checking the power supply first. This manual makes you check the fuse data and wire size conversion chart (page 5 has the metric-to-AWG table) before you start probing. That is the difference between a five-minute diagnosis and chasing a ghost all afternoon.

Injection Electronics S38 Engine: What the Manual Covers

Section 1362 covers the injection electronics for the S38 engine found in the M6. Section 1360 covers the 3.5L engine in the L6. These are not generic fuel injection diagrams. They show every connector pin, every splice location, and every ground path. If you have a no-start or a stumble, you need the component location views (section 7000) and the splice location views (section 8000) to trace the harness. Without these, you are reading A through R on a bad photocopy and praying. This manual gives you the real thing.

ABS Diagnostics: Factory Procedure

Section 3450 covers the Antilock Braking System. The Brake lining warning is section 3435. If you are troubleshooting an ABS fault, you need the exact wire colors and the test points at the control module. The manual shows the entire circuit from the wheel speed sensors to the hydraulic unit. I have seen aftermarket diagrams miss a ground splice that causes intermittent codes. This OEM manual does not miss anything.

Does This Manual Cover the Self-Leveling Suspension?

Yes. Section 3700 is dedicated to the self-leveling suspension. It includes the electrical connections to the level sensors and the control unit. If your M6 sits low in the rear or the compressor won’t run, you need to verify the signal paths. The component location chart (section 9000) tells you exactly where each sensor lives. Combined with the connector views (section 8500), you can confirm continuity without pulling half the trunk apart.

3 Reasons to Choose OEM Documentation Over Aftermarket

First, the wire colors are BMW factory codes — BK, BR, RD, YL, GN, BU, VI, GY, WT, PK — not guesses. Second, the systematic troubleshooting method on page 6 gives a repeatable sequence: power distribution, ground distribution, then circuit test. Third, the part numbers for connectors and fuses are original BMW numbers. You can order the right parts without cross-referencing. Aftermarket manuals often combine years and lose critical details, like the 1987 vehicles built before 9/86 using the 1986 635CSi manual. That note is on page 1 of this book.

Transmission and Other Electrical Systems

Section 2460 covers the electronic Transmission control. If the shift points are off or the transmission goes into limp mode, you need to check the sensors and solenoids. The manual gives the full wiring for the electronic transmission control. For the Electrical body, section 6100 through 6581 covers everything: power mirrors, central locking, power windows, seats, sunroof, wipers, instrument cluster, active check control, lights, A/C, cruise control, and on-board computer. Every circuit is on its own schematic. No need to flip back and forth between unrelated pages.

Source Validity: Factory Print, Not a Reprint

This is an authentic BMW of North America troubleshooting manual, part number PN 89 99 1 000 167. Printed in 1987. It is not a third-party compilation. The foreword on page 2 states that designs may change, so the manual is vehicle-specific. If you are working on a 1987 L6 or M6, this is the only electrical troubleshooting document you should trust. All other manuals are copies of copies. Get the original at 1988 BMW 635CSi/M6 Electrical Troubleshooting Manual if you need the next year, or check the BMW 525i/535i 1989 Troubleshooting Manual – Factory Specs for other models. For a earlier 3-series, see 1986 BMW 325 Troubleshooting Manual – OEM Electrical Guide. For general background on automotive electrical systems, refer to Automotive Industry Overview and Manual Transmission for drivetrain basics.

Is this manual specific to the 1987 L6 and M6?

Yes. It covers 1987 L6 and M6 models. Vehicles built before 9/86 use the 1986 635CSi manual.

Does it cover the 3.5L and S38 engines?

Section 1360 covers injection electronics for the 3.5L engine (L6), and section 1362 covers the S38 engine (M6). Both include full wiring diagrams, component locations, and connector pinouts. You also get the start system (section 1240) and charging system (1230) to diagnose cranking and charging issues.

What about the automatic transmission?

Section 2460 covers the electronic transmission control. The manual includes the shift solenoid circuits, speed sensor wiring, and the control module connections. If your transmission has electrical faults, this is the section you need.

Are wiring diagrams included for the entire car?

Every electrical system is covered from power distribution (0670) to the radio antenna (6500). That is 188 pages of schematics, component location views (7000), splice views (8000), and connector views (8500). The systematic troubleshooting method on page 6 teaches you how to read and use them.

You need the right data to fix these cars. Don’t waste time on generic wiring charts or online forums where someone guessed the pinout. Access the Factory Manual now and get the exact specifications that BMW engineers intended.