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JOHN aka Eauto
JOHN aka Eauto, The Car Guy
Category: Chevy
Satisfied Customers: 16100
Experience:  ase tech
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1998 Chev 2500, 4L80E transmission, fault code P1860,

Customer Question

1998 Chev 2500, 4L80E transmission, fault code P1860, already replaced TCC solenoid and checked wiring to trans.
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
Clear fault code and it will shift into 4th and tcc locks up but in very short time the fault comes back and goes back to 3rd gear. After clearing fault, watch scan tool and tcc enables duty cycle about 99, slippage low at about 2, then it messes up and tcc is disabled and goes to 3rd gear.
Expert:  JOHN aka Eauto replied 1 year ago.

have you checked the connector and circuit for damaged pins or wiring issues?

Customer: replied 1 year ago.
checked both side of connector with other pins and all feel good. Nothing bent or broken. Hooked up a tail light to tcc wiring and can turn that on and off with scan tool.
Expert:  JOHN aka Eauto replied 1 year ago.

The Torque Converter Clutch Width Modulation Solenoid Valve (TCC PWM Solenoid Valve) controls fluid acting on the converter clutch valve, which then controls TCC apply and release. The TCC PWM Sol. Valve attaches to the control valve body within the transmission. Ignition voltage goes directly to the TCC PWM Sol. Valve. The Vehicle Control Modulator (VCM) controls the TCC PWM Sol. Valve by providing a ground path on circuit 418. The current flows through the TCC PWM Sol. Valve coil according to the duty cycle (percentage of ON time). The TCC PWM Sol. Valve provides a smooth engagement of the torque converter clutch by operating on a duty cycle percent of ON time.

If the VCM detects a continuous open or short in the TCC PWM Sol. Valve circuit or the TCC PWM Sol. Valve, then DTC P1860 sets. DTC P1860 is a type D DTC. For California emission vehicles DTC P1860 is a type A DTC.

Customer: replied 1 year ago.
i do not see a power train OBD system checks on my scanner. My scanner is a snap solus.
Expert:  JOHN aka Eauto replied 1 year ago.

need a tech 2 maybe snap n has it under a functional test?

Customer: replied 1 year ago.
Ok functional test...any ideas what it is callled? Otherwise I need a technician with solus experience.
Customer: replied 1 year ago.
If I follow the rest of the trouble shooting charts, it brings me down to diagnostic aid.
Expert:  JOHN aka Eauto replied 1 year ago.

for which step?

Customer: replied 1 year ago.
Step 1: OBD system check - can't do.
Step 2: Fuse open - no. Go to step 4.
Step 4: test lamp on - yes. Go to step 6.
Step 6: test lamp on and off - yes. Go to step 8.
Step 8: resistance within - yes. Go to step 11..
Step 11: both readings greater than - yes. Go to diagnostic aids.
So answer to your question of which step, it would be step 11.
Expert:  JOHN aka Eauto replied 1 year ago.
  1. Remove the fuse to the circuit involved.
  2. Connect one lead of a self-powered test light or ohmmeter to one end of the part of the circuit you wish to test.
  3. Connect the other lead to the other end of the circuit.
  4. If the self-powered test light glows, there is continuity. When using an ohmmeter, LO or no resistance means good continuity.
Expert:  JOHN aka Eauto replied 1 year ago.


  1. Remove the blown fuse and disconnect the load.
  2. Connect a test light or voltmeter across the fuse terminals (be sure that the fuse is powered).
  3. Beginning near the Fuse Block, wiggle the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the test light or DVM.
  4. When the test light glows, or the DVM registers, there is a short to ground in the wiring near that point.
Expert:  JOHN aka Eauto replied 1 year ago.

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