P07F3

Code

Generic P — Powertrain

Transmission Range Control Module Communication Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 18 EN: 27 RU: 16

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Page language: EN

Causes

Damaged or shorted communication wiring (short to ground)
Corroded, loose, or damaged connector at the TRCM or network splice
Poor or missing module ground or low supply voltage to TRCM
Failed or intermittent TRCM (internal circuit fault)
Faulty termination resistor(s) or missing CAN/LIN termination
Network interference from another module or accessory

Symptoms

Malfunction Indicator Lamp (MIL) or transmission-related warning lamp illuminated
Transmission may enter limp/backup mode or default to a single gear
Gear selection indicator incorrect or not displayed
Loss of certain transmission functions (shift irregularities, no starts in park/neutral on some vehicles)
Other modules reporting communication errors or related fault codes

What to check

Scan for stored/active codes and capture freeze-frame and live data
Check for other network-related U-codes indicating wider bus issues
Visually inspect TRCM connector, pins and wiring for corrosion, damage, or water intrusion
Verify vehicle battery voltage and TRCM power and ground integrity
Measure communication bus voltages at the TRCM connector with key on, engine off
Check resistance across CANH–CANL (or LIN bus to ground) with ignition off

Signal parameters

CAN bus (if used): recessive ~2.5 V on CANH and CANL; dominant ~CANH 3.5 V / CANL 1.5 V (approximate)
CAN bus characteristic resistance: ~60 Ω measured across CANH–CANL (two 120 Ω terminations in parallel)
LIN bus (if used): recessive typically pulled to battery voltage via pull-up; dominant ≈ 0 V (single-wire)
Data: normal periodic activity and voltage transitions when bus is healthy
A 'low' communication circuit typically measures lower than expected recessive voltage or near ground

Diagnostic algorithm

Read and record all related codes and freeze-frame data. Note if other modules report bus faults.
Check battery voltage and inspect TRCM power and ground pins for good connection and correct voltage.
Visually inspect connector and wiring for damage, corrosion, water, or pin push-out. Repair as needed.
With ignition ON (engine off), measure voltages on the communication pins at the TRCM connector and compare to expected parameters for CAN or LIN. Look for stuck-low conditions.
Measure resistance across CANH–CANL with ignition OFF; expect ~60 Ω. Infinite or very high indicates open/missing termination; near 0 Ω indicates short.
If network shows low voltage on one line, isolate by disconnecting modules one at a time (if safe) to find which segment pulls the line low.
Perform pin-to-pin continuity and short-to-ground tests between TRCM and PCM/BCM connectors using wiring diagrams to pinpoint wiring faults.
If wiring and power/ground check good, swap or bench-test TRCM if a known-good unit is available (or inspect for internal damage) and reflash module software if recommended.
Repair or replace damaged wiring, connectors, or module. Reinstall correct termination resistors if missing.
Clear codes and road-test to confirm repair. Re-scan to verify no recurrence.

Likely causes

Corroded/poor connector or pin at the TRCM
Short to ground in the communication wire between TRCM and the network
Failed TRCM
Missing or open ground or low module supply voltage

Fault status

⚠️ Status

Transmission Range Control Module communication circuit low — the TRCM's communication line is reading below expected voltage, causing loss or degradation of network communication.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours