Fitment notes: Battery located in engine compartment; European H8 specification may also fit
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Every control module on the 1986-1991 Mercedes-Benz 420SEL — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
Climate Control Module (KE)2.5 hr R&Rno coding
📍 Behind center dashboard climate control panel
⚠️ Electronic climate control; self-diagnostic mode accessible via button sequence; no external coding
Instrument Cluster (IC)2.0 hr R&Rno coding
📍 Dashboard behind instrument panel
⚠️ Analog cluster with electronic speedometer; odometer mileage stored mechanically; no coding required
Anti-Lock Brake System Control Unit (ABS)1.8 hr R&Rno coding
📍 Engine compartment, right side near fender or under hood near master cylinder
⚠️ Bosch ABS 2 system; bleeding procedure critical after replacement; no coding but may require fault code clearing
Transmission Control Unit (TCU)1.5 hr R&Rrelearn only +0.3 hr▸ programming details
📍 Under driver's seat or behind center console kick panel
🔧 Bosch KTS or Mercedes HHT
⚠️ 4-speed automatic (722.3/722.4); shift point adaptation required after replacement
Engine Control Unit (ECU)1.2 hr R&Rrelearn only +0.3 hr▸ programming details
📍 Engine compartment, left side firewall near brake booster
🔧 Bosch KTS or Mercedes HHT
⚠️ Bosch KE-Jetronic with electronic control; idle speed and basic adaptations only; fault code reading via 38-pin connector
Supplemental Restraint System Control Unit (SRS)1.0 hr R&Rno coding
📍 Under center console between front seats
⚠️ Introduced mid-1988 model year; battery disconnect mandatory; no coding but fault memory must be cleared
⚠️ Introduced 1990 model year; early immobilizer system; key coding required with dealer tool
Cruise Control Module (CC)0.8 hr R&Rno coding
📍 Engine compartment, left side near ECU or integrated into ECU
⚠️ May be integrated into ECU on later models; standalone module on earlier years
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 1987 Mercedes-Benz 420SEL 4.2L V8 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years.