SERVICE MANUAL UPDATE-SEC.8A CRUISE CONTROL DIAG. UPDATE

SUBJECT: SERVICE MANUAL UPDATE SECTION 8A CELL 34 CRUISE CONTROL (UPDATE ON DIAGNOSIS)

VEHICLES AFFECTED: 1987 - 1990 V, E AND K MODELS

Please update your 1987-1989 Allante Service Information Manuals and 1990 Eldorado and Seville Service Information Manual, Section 8A cell 34, to include the following information regarding inoperative cruise control diagnosis.

The VCC brake switch and the stop lamp/cruise switch are inputs to the ECM (E171 and E170 respectively). An open in either switch could result inoperative cruise control or cruise control that intermittently will not operate. The affected models should include the VCC brake input E171 as shown in Figure 1.

Additionally the 1987-1988 edition of the Allante Manual, page 8A-34-0, indicates "Cruise Enable Input" E178. This input should be "Cruise Brake Input" E170. This page should also include "VCC Brake Input" E171 as shown in Figure 1.

The procedure in Table 1 (below) should be included in all cruise control system diagnosis for the affected models.

CRUISE CONTROL IS INOPERATIVE (TABLE 2)

Enter: ECM DIAGNOSTICS Select: ECM INPUT TEST E170 Condition: o Cruise Switch - ON ----------------------------------------------- ECM For Action Displays Diagnosis =============================================== Depress Brake Pedal LO See *1

----------------------------------------------- Release Brake Pedal HI See *1

----------------------------------------------- o If ECM displays are correct, go to Table 3.

*1. Refer to ECM Input Test E170, Section 8D1. -----------------------------------------------

Select: ECM INPUT TEST E171 ============================================== Depress Brake Pedal LO See *2 ----------------------------------------------- Release Brake Pedal HI See *2 ----------------------------------------------- o If ECM displays are correct, go to Table 3.

*2. Refer to ECM Input Test E171, Section 8D1. ----------------------------------------------- Table 1

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.