BMW 325i, 325is, 325e, 325, 325es 1987 Troubleshooting Manual – Factory Electrical Diagnostics

If you’re chasing an electrical gremlin on a 1987 BMW 325, 325e, 325es, 325i, or 325is, you already know the aftermarket wiring diagrams are garbage. I’ve seen guys spend a full day tracing a no-start because the third-party schematic swapped the starter relay pinout. This factory BMW 325i, 325is, 325e, 325, 325es 1987 Troubleshooting Manual (173 pages, published 1987) is the only document that matches the actual harness colors and splice locations. Don’t trust a reprint from some online library—get the OEM print.

0670 Power Distribution: Fuse Data and Box Layouts

Power distribution is where most electrical problems start. The manual breaks this out by engine: 2.7e and 2.5i, with separate diagrams for convertible models. Page 4 of the index gives you a quick lookup for every circuit. The fuse data chart (0670-1) lists each fuse’s amperage, circuit name, and which components it feeds. Working on a 325i convertible? You get a dedicated power distribution box layout that matches the underhood box exactly—no guessing which relay is which.

1230 Charge 2.7e Engine – How It Differs from the 2.5i

Generators and voltage regulators behave differently between the eta and i engines. Section 1230 covers the charge system for the 2.7e (eta) engine. If you’re diagnosing a battery drain or charging issue on a 325e, you need the exact pinout for the generator connector. This manual gives you the wire colors and test points. The 2.5i charge system is in a separate subsection—don’t mix them up or you’ll be chasing a phantom problem.

1360 Injection Electronics 2.5i Engine – Troubleshooting Steps

Injection electronics (Motronic) on the 2.5i engine can throw codes that look like mechanical failures. Section 1360 walks you through the ECU pin signals, injector pulse width checks, and sensor voltage readings. No shortcuts here: you’ll find the necessary test equipment listed. For the 2.7e engine, section 1362 covers the different ECU and engine management variant. Having both in one manual saves you from buying two separate books.

3450 Antiblock Braking System (ABS) – Factory Diagnostic Flow

ABS problems on these cars often get misdiagnosed as wheel speed sensor failures when it’s actually a relay or controller issue. Section 3450 gives you the factory diagnostic sequence—start at the ABS control unit, check power and ground, then wheel speed sensor resistance. The wiring diagrams are color-coded like the actual harness. I’ve used this to find a corroded splice in the left rear sensor circuit that three aftermarket diagrams missed.

7000 Component Location Views – Don’t Waste Time Hunting Parts

Component location views (section 7000) show you exactly where every relay, module, and sensor lives. Need the cruise control module? Not under the dash like you’d guess—it’s behind the glove box on the 2.5i. This manual puts drawings with real-world positions. The splice location views (section 8000) cover both convertible and non-convertible versions, and differentiate by 2.7e and 2.5i engine harnesses. If you’re splicing in a new wire, you’ll know which splice pack to look for without pulling half the interior.

Why OEM Documentation Beats Aftermarket Reprints

I’ve been turning wrenches since 1985. Every aftermarket electrical manual I’ve ever seen for these BMWs has errors—wrong wire colors, swapped pin numbers, missing connector views. The factory manual from BMW of North America (PN 01 00 1457 820) is the actual document their dealerships used. It includes the important note: 1987 vehicles built before 9/86 must use the 1986 325 Electrical Troubleshooting Manual. That kind of precision keeps a technician from frying an ECU. The 1987 version you get here has 173 pages of verified information, not a photocopy of a photocopy.

For understanding the broader context of automotive electrical systems, refer to Automotive Industry Overview. And if you need general transmission info, Manual Transmission covers the basics—though this manual focuses only on electrical.

Related Manuals

• BMW 3 Series 1999-2005 Service Manual
• BMW 3 Series 1992-1998 Service Manual
• BMW 318i 318is 325i 325is 1993 Electrical Troubleshooting Manual

Does this manual cover the convertible models?

Yes, separate sections for convertible are included throughout.

What if my car was built before September 1986?

The manual explicitly states on page 1 that vehicles built before 9/86 must use the 1986 325 Electrical Troubleshooting Manual for diagnostics. The wiring harnesses changed mid-year. Using this 1987 manual on an early 1986 car will give you wrong pin assignments. Always check the build date on the driver’s door jamb sticker. I’ve had two cars come in where someone used the wrong year manual and fried the ECU. Don’t be that guy.

Stop chasing ghosts with aftermarket copies that have swapped pinouts. Download the Factory Manual and get the exact wiring diagrams BMW intended for your 325, 325e, 325es, 325i, or 325is.