Replaces the shift A/B, 3-2 downshift, EPC, PWM and TCC solenoids plus the internal harness on a GM 4L60E in one kit, so no old solenoid is left behind.
Brittle wires, a cracked connector lock, or a TCC slip code that keeps coming back after one solenoid was already replaced: that is the situation this kit was put together for. It replaces all six valve body solenoids on a GM 4L60E plus the internal wiring harness the TCC solenoid hangs from, so a high-mileage Silverado, Sierra, Tahoe, Yukon, Express or Camaro leaves the shop with no original electrical part left on the valve body. The same layout is shared by the 4L65E and 4L70E, and the kit is sold for all three. The manufacturer part number is 99138.
Inside the pan, a single internal harness runs from the case pass-through connector to every solenoid on the valve body. The PCM uses it to switch shift solenoids A and B for gear selection, pulse the EPC solenoid to set line pressure, fire the 3-2 solenoid for kickdown timing, and command the TCC and PWM solenoids that apply and smooth converter lockup. Because the harness lives in hot fluid for its whole life, its insulation hardens and its connector tabs crack. A wire that only opens when warm will set a solenoid code that looks exactly like a failed solenoid, which is why replacing the harness along with the solenoids matters.
Pull codes and note whether they are performance codes (the gear ratio was wrong) or circuit codes (the PCM saw an electrical fault). Circuit codes on several solenoids at once almost always point at the shared harness or connector, which this kit covers. Performance codes with good solenoid resistance can also be valve body wear: Sonnax notes that bore wear is common in this family and recommends a vacuum test before guessing. Our shift solenoid A and B code guide explains the difference, and the P0748 pressure control guide covers the EPC side.
Published references for this part mix year ranges (1993-2002 PWM, 2003-up and 2009-on), so do not order on the year alone. Compare the TCC and PWM solenoids and the EPC connector against the parts on your valve body before installing. Early 1993-1995 4L60E units used a different converter clutch setup and may not match. If you are unsure, send your year and VIN and we will check it. Year-specific kits for every 4L60E range are listed on the 4L60E parts page.
Drain and drop the pan, pull the filter, and release the case connector from the pass-through. Photograph the harness routing and clip positions before removing anything. Remove the retaining clips on shift solenoids A and B, unbolt the EPC and 3-2 solenoids, and lift the TCC and PWM solenoids out with the old harness. Lube each O-ring with clean ATF, torque the solenoid and valve body bolts to spec, and clip the new harness exactly where the old one sat so it cannot rub on the manual valve linkage. GM's own service bulletin PIP5009G told technicians on 2012 trucks to replace the internal harness and TCC enable solenoid any time transmission repairs were performed, which says a lot about how often these harnesses fail. Refill with Dexron VI, then run a shift relearn or idle shift check before road testing. If you are already in the valve body for firm-shift complaints, a 4L60E shift kit goes in at the same time; if vacuum testing shows worn bores, a refurbished valve body with solenoids is the better fix.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The internal harness sits in hot fluid and its insulation and connector locks harden and crack over time. An open wire sets the same codes as a dead solenoid, so replacing both removes the most common reason for a repeat failure.
The kit is sold for the 4L60E, 4L65E and 4L70E because they share the valve body solenoid layout. Compare the TCC, PWM and EPC solenoids and connectors to yours before installing.
Possibly not. Early 1993-1995 4L60E units used a different torque converter clutch setup. Send your year and VIN so fitment can be confirmed before you order.
It fixes P1870 when the cause is the TCC or PWM solenoid or the harness. On many high-mileage units P1870 comes from worn valve body bores, which a vacuum test will reveal; in that case the valve body needs attention too.
Refill with Dexron VI ATF. Clear codes and run a shift relearn or let the PCM adapt over several drive cycles, then road test through all gears and lockup.
