B1877

Code

LAND ROVER B — Body

Control of the deployment of the left seat belt pretensioner - open circuit

Brand: LAND ROVER

Type: B — Body

Views: UK: 21 EN: 29 RU: 22

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Page language: EN

Causes

Damaged or disconnected pretensioner connector at the seat
Broken wiring / open conductor between pretensioner and SRS control module
Corroded or bent pins in connector
Failed pretensioner squib (open internal element)
Faulty SRS control module or poor connection at module
Blown related fuse or poor ground in SRS circuits

Symptoms

SRS / airbag warning lamp illuminated on dash
Left seat belt pretensioner will not deploy in an event (system disabled)
Possible additional SRS-related DTCs stored
No obvious electrical behavior until scanned (passive fault)

What to check

Scan SRS control module for B1877 and any related codes; record freeze frame/live data
Visually inspect left seat pretensioner connector and wiring for damage, corrosion, or disconnection
Check continuity/resistance of pretensioner circuit between SRS module and pretensioner (with safety procedures)
Check for proper ground and fusing in SRS supply circuits
Wiggle seat while monitoring fault to check for intermittent opens in harness
Confirm SRS warning lamp behavior and that the control module is powered

Signal parameters

Circuit continuity: intact circuit shows low resistance; open circuit shows infinite/OL
Squib/pretensioner resistance: low (typically a few ohms — refer to manufacturer spec for exact value)
Voltage: normally no steady battery voltage present at squib connector; module supplies firing voltage only during deployment
SRS lamp: ON when SRS control module detects open circuit fault
Fault memory: B1877 stored in SRS control module with occurrence count

Diagnostic algorithm

Safety first: disable vehicle battery and follow the manufacturer's specified wait time for SRS system discharge before touching connectors or the pretensioner.
Use a diagnostic scan tool to read and record all SRS/airbag DTCs and freeze frame data. Note any additional related DTCs.
Visually inspect the left seat pretensioner connector, wiring harness (especially at seat base and adjuster points), and module connector for damage, corrosion or loose pins.
With battery still isolated, disconnect the pretensioner connector and inspect pin condition. Reconnect firmly if pins are OK.
Measure continuity/resistance of the pretensioner circuit between the SRS control module connector and the pretensioner squib. An open (OL) indicates a wiring or connector break; low resistance indicates intact squib.
Check for short to battery or short to ground on the circuit if resistance is lower/higher than spec. Wiggle wiring to check for intermittent opens.
If wiring and connectors are good but squib shows open, replace the pretensioner with a genuine/or-specified unit.
If wiring is open or damaged, repair wiring or replace harness section using correct crimping/soldering, insulation, and routing to avoid future damage. Re-pin or replace connectors if required.
After repairs, clear codes with a scan tool, reconnect battery, and perform SRS lamp check and any manufacturer-specified self-tests or relearns.
If fault persists after logical wiring/pretensioner replacement, suspect SRS control module fault and follow manufacturer procedure for module testing/repair or replacement.

Likely causes

Open or broken wire in seat harness (seat movement area common failure point)
Disconnected or corroded connector under the seat
Damaged pretensioner due to prior deployment or impact
Connector pin pulled out or shorted internally
Intermittent open due to seat position/adjuster movement

Fault status

⚠️ Status

B1877 — Left seat belt pretensioner circuit open. SRS control module detects loss of continuity; left pretensioner disabled. Check connectors, wiring, and pretensioner squib.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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B1877 — Control of the deployment of the left seat belt pretensioner - open circuit