Code
P1689
PONTIAC
P — Powertrain
No Communication Between ECM & Injection Pump Module
Views:
UK: 19
EN: 38
RU: 34
AI status
Completed
Completed
100%
Causes
- Open, shorted or corroded wiring between ECM and injection pump module (CAN/Class 2/serial bus)
- Faulty injection pump control module
- Faulty ECM/PCM
- Blown fuse or loss of module power or ground
- Poor connector pin contact or water intrusion at one of the modules
- Network termination resistor missing or shorted
Symptoms
- MIL/Check Engine lamp illuminated
- Engine may crank but not start or run poorly (diesel common)
- Reduced engine power or limp-home mode
- No response from injection pump when commanded
- Other network modules reporting communication faults
- Difficulty performing module programming or calibration via scan tool
What to check
- Read stored and pending DTCs with a capable OEM scan tool; note freeze frame data
- Confirm whether scan tool can communicate with ECM and the injection pump module separately
- Inspect fuses and relays supplying pump module and ECM for continuity
- Visually inspect wiring harnesses and connectors for damage, corrosion, or fluid intrusion
- Check battery voltage and good engine/chassis grounds before starting communications tests
- Backprobe module power and ground pins while key ON; confirm proper voltages
Signal parameters
- Battery system voltage: typically 12.2–14.7 V with engine running
- Module ground resistance to battery negative: ideally
- CAN bus recessive voltage (each line): approx. 2.5 V
- CAN bus dominant voltages: CANH ≈ 3.5 V, CANL ≈ 1.5 V (differential ≈ 2 V)
- Termination resistance across CANH–CANL: approx. 60 ohms (two 120 ohm terminators in parallel)
- Injector pump module supply fuse: continuity (no open circuit)
Diagnostic algorithm
- Verify DTC: Connect an OEM-capable scan tool, record P1689 and any related codes, and capture freeze-frame.
- Check power/ground: With key ON, measure supply voltage and ground at the injection pump module connector; repair any open/corroded feed or ground.
- Inspect connectors/wiring: Visually and physically inspect harnesses between ECM and pump for damage; repair or replace damaged sections.
- Verify network: Measure CAN or serial bus voltages at both the ECM and injection pump module. Confirm termination resistance (~60 ohms).
- Isolation testing: Disconnect downstream modules/connectors and observe if communication returns to isolate a shorted device or harness section.
- Wiggle/wear test: With scan tool monitoring communication, wiggle wiring and connectors to reproduce intermittent faults.
- Scope test: If available, use an oscilloscope to view CAN waveforms for noise, missing packets or bus-off conditions; look for dominant/recessive transitions.
- Check for software issues: Verify correct calibration/programming levels; reflash or update module software if required by service information.
- Replace/repair: If wiring and power/grounds are verified good, replace or reprogram the failed injection pump module (or ECM if identified) per factory procedures.
- Verify repair: Clear codes, perform relearn/programming as required, and test drive/operate to confirm the communication fault is resolved.
Likely causes
- Damaged connector or corroded pins at injection pump module
- Blown fuse or poor power/ground to the injection pump module
- Open/short in CAN or serial communication wires between ECM and pump module
- Failed injection pump control module
- Network wiring shorted to battery or ground
- ECM communication port fault or corrupted software
Fault status
Status
No communication between ECM and Injection Pump Module — message missing on vehicle network.
Repair difficulty: Medium
Diagnostic time: 1.5-3.0 hours
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