U2002

Code

HUMMER U — Network/User

SPI Data-In Low

Brand: HUMMER

Type: U — Network/User

Views: UK: 8 EN: 12 RU: 10

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Page language: EN

Stored U2002 code and related network communication codes
Loss of functionality for systems served by the SPI network (dependent on vehicle)
Intermittent errors or limp‑in mode for affected modules
No engine mechanical issues solely from this code, but dependent features may be inoperative
Possible hard or soft faults after key cycles or reprogramming

Read all modules with a capable scan tool and note related U‑codes and freeze frame data
Verify vehicle battery voltage and ground integrity before testing
Visually inspect harness and connectors for damage, corrosion, or bent pins on modules using the SPI bus
Backprobe the SPI Data‑In pin at the affected module and at intermediate connectors
Measure DC voltage on SPI data line (key ON, engine OFF) and compare to expected idle level
Use an oscilloscope to observe data line activity and look for it being held low

Idle voltage: expected HIGH at approximately VCC (commonly 3.3 V or 5 V depending on module); LOW is near 0 V
Low threshold: typically
High threshold: typically >0.7 × VCC is interpreted as logic HIGH
SPI clock and data are digital pulses — use an oscilloscope to verify clock and data transitions and timing
No/very low data line activity when the bus is held low

Connect a professional scan tool; record freeze frame, accompanying U‑codes, module firmware levels and number of events.
Confirm basic power and ground: measure battery voltage and check engine/chassis grounds at modules using SPI bus.
Visually inspect connectors and wiring for damage or corrosion between the reporting module and other SPI nodes; repair any physical damage.
With key ON, backprobe the SPI Data‑In pin at the reporting module. Measure DC voltage. If the line is near 0 V, suspect a short to ground or a module pulling it low.
If DC low is present, disconnect suspect modules (one at a time) from the SPI network while monitoring the data line to identify which module causes the line to be held low.
Use an oscilloscope to confirm absence/presence of clock and data pulses and verify whether the line is actively driven low or simply shorted.
Check continuity to pull‑up/termination resistors and verify resistor values per service data; repair or replace failed resistors.
If wiring and passive components test good, swap or replace the module identified as driving the line low (per manufacturer's procedures) or reprogram firmware if appropriate.
Clear codes, perform functional tests and road test to verify repair. Re-scan for related codes and confirm stability across key cycles.

⚠️ Status

SPI Data‑In line is held low — device cannot receive SPI data.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours

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U2002 — SPI Data-In Low