Code
P1172
HUMMER
P — Powertrain
Fuel Transfer Pump Flow Insufficient
Views:
UK: 26
EN: 38
RU: 34
AI status
Completed
Completed
100%
Causes
- Failed or weak fuel transfer pump
- Clogged fuel filter/strainer or in-tank pickup screen
- Restricted, kinked or collapsed fuel lines
- Faulty check/one-way valve or stuck transfer valve
- Electrical problem: blown fuse, bad relay, damaged wiring or poor connector
- Low battery/insufficient supply voltage during pump operation
Symptoms
- MIL (Check Engine Light) illuminated
- Poor or irregular fuel transfer between tanks (if vehicle has dual tanks)
- Long cranking, hard start or stalling after start
- Reduced fuel pressure at engine or limp performance
- Fuel gauge or tank-level switching issues (on dual-tank systems)
- Noise from fuel tank area (weak or no pump sound when commanded)
What to check
- Read freeze-frame and live data with a scan tool; note related codes
- Verify fuse(s) and relay(s) for transfer pump circuit
- Inspect wiring harness and connectors at pump and PCM for corrosion, damage and proper seating
- Listen for pump operation when commanded (key on / active test)
- Measure voltage at pump connector during commanded operation
- Measure current draw of transfer pump (compare to spec)
Signal parameters
- Pump supply voltage when commanded: ~11–14 V (depends on battery/engine running); must be within manufacturer spec
- Control signal may be direct battery switched or PWM from module — verify presence of control voltage when commanded
- Pump current draw under normal load: consult service manual; an abnormally low current often indicates motor failure, abnormally high indicates mechanical restriction or binding
- Fuel flow rate expected: consult model-specific service values for liters/min or gallons/hour
- No continuity or open circuit between pump and ground suggests wiring fault
Diagnostic algorithm
- Connect a scan tool, record P1172 and any related codes; view freeze-frame and live data for fuel pump/transfer status.
- Visually inspect fuses, relays and connectors for the transfer pump; repair any obvious damage or corrosion.
- Using an active test (if available), command the transfer pump on and listen/observe for operation. If no operation, measure voltage at the pump connector while commanded.
- If voltage is present but pump does not run, measure pump current. Low/no current with proper voltage indicates a faulty pump; high current can indicate mechanical restriction.
- If pump runs but flow is low, inspect and/or replace fuel filter, strainer and in-tank pickup screen; inspect transfer and vent lines for kinks or restrictions.
- Inspect transfer/check valves and tank switching components for proper operation; clean or replace as required.
- If electrical supply is intermittent or low, trace wiring back to relay/PCM; perform back-probing and continuity/resistance checks between pump, relay and PCM.
- If wiring and external components test good but pump performance remains out of spec, remove and bench-test or replace the transfer pump assembly per service procedure.
- After repair, clear codes and perform a road test and transfer cycle(s) to confirm proper flow and that P1172 does not return.
Likely causes
- Clogged transfer filter or pickup screen
- Failed or mechanically weak transfer pump
- Open/short or high resistance in pump supply or ground circuit
- Restricted fuel line or collapsed hose between tanks
- Faulty pump relay or fuse
- Stuck transfer/check valve preventing flow
Fault status
Status
Fuel Transfer Pump Flow Insufficient — transfer pump delivering less than expected flow; inspect pump, filters, lines and electrical supply.
Repair difficulty: Medium
Diagnostic time: 1.0-4.0 hours (model and access dependent)
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