CHECK ENGINE LIGHT CODE 34 DIAGNOSIS INFORMATION LISTED

1985 6000 AND FIREBIRD MODELS WITH LB6 AND LB8 2.8L V6 MFI ENGINES (VIN CODES W AND S)

Customer comments may be received on certain 1985 cars with the 2.8L-V6 MFI engine regarding check engine light (Code 34), engine surge or hesitation. Listed below is information that should help to correct each condition.

Item #1. Check Engine Light (Code 34) ------------------------------------ Code 34 will set if the following conditions are met:

Engine running

Mass Air Flow Sensor (MAF) disconnected, faulty MAF relay or MAF signal circuit shorted to ground.

OR

Air flow less than 2 grams per second (low frequency)

To correct a Code 34 check engine light, first make sure that the MAF Relay is working and supplies + 12 volts to the MAF Sensor. This can be accomplished by connecting a test lamp between ground and the "+" terminal of the MAF Sensor harness. With the ignition "ON," the test lamp should light. If the lamp doesn't light, check for an open in the + 12 volt supply or a faulty relay.

If power is supplied to the MAF sensor, use the standard fault tree for check engine light (Code 34) in Section 6E3 of the Service Manual.

Item #2. Engine Surge --------------------- Item #2A -------- If the vehicle exhibits surge, follow procedures in Section B - Symptoms, Section 6E3 of the Service Manual for diagnosing surge. Particular attention should be given to:

Checking rear spark plug wires for heat damaged wires. Replace if damaged.

Checking spark plug wire boots for evidence of carbon tracking. If carbon tracking is present in spark plug boot replace both spark plug and spark plug wire.

Item #2B -------- If the surge is not corrected, installation of the later production parts should correct the condition.

Install the latest PROM unless the ECM already has it. (This can be done by using Chart I).

The latest PROM has revised EGR scheduling when the torque convertor is engaged. This should reduce surge (TCC chuggle).

If the car is a Pontiac 6000 or STE, install a new air cleaner housing which utilizes a honey-comb air flow screen. This is provided in a service kit (P/N 25097022) which contains the air cleaner housing, gasket, and clamp.

After installing this new housing the car should be parked and the engine allowed to cool to ambient temperature; then cold started and driven a minimum of three miles to update the ECM memory.

NOTICE: During the first cold start after installing the new air cleaner housing the engine may hesitate and possibly backfire until the ECM memory is updated.

Item #3. Engine Hesitation --------------------------- If the engine exhibits hesitation during acceleration when the engine is cold, install the following parts to correct the problem.

Install the latest PROM unless the ECM already has it. (This can be done using Chart I).

If the vehicle has early production injectors, install the revised injectors which have a revised spray pattern. The new injector is part of a kit P/N 17111297; six (6) kits required per engine.

NOTICE:Injectors with the correct spray pattern have already been installed on engines with a build date code of 0107 (January 7th) or later.

Example: T 01 07 CAF

This code is stamped on the horizontal machined surface of the block just forward of the intake manifold.

If the engine continues to exhibit a hesitation after the preceding changes, follow procedures for hesitation diagnosis in Section 6E3 of the Service Manual.

NOTICE: One of the steps in the Service Manual is to perform the injector balance test. It is important that this test be performed to identify restricted injectors. If the injectors are plugged or restricted, clean the injectors using recommended service procedures.

Warranty Information

Reference Chart II.

CHART I: PROCEDURE TO IDENTIFY AND INSTALL LATEST PROM

Procedure

If scan tool is available, determine PROM I.D. using a scan tool, find scan data in Column A of the following chart and perform action in Column C.

If scan tool is unavailable, remove ECM from vehicle and determine PROM I.D. by visually inspecting PROM. Find PROM code in Column B of the following chart and perform action in Column C.

A B C AIR SCAN TOOL PROM I.D. SALES MODEL TRANS. AXLE COND. DATA IN VEHICLE ACTION ----- ----- ------ ---- ----- ---- ---------- ------ FED 6000 A.T. (MD9) 2.84 Yes 6961 2412 CHS Install Service P/N 16049780 9381 9781 FPH NO ACTION

FED 6000 A.T. (MD9) 2.84 No 3731 4726 DTK Install Service P/N 16052572 9721 2573 FRZ NO ACTION

FED 6000 A.T. (MD9) 3.18 Yes 3741 4731 DTL Install Service P/N 16052577 9731 2578 FSA NO ACTION

FED 6000 A.T. (MD9) 3.18 No 3751 4736 DTM Install Service P/N 16052584 9741 2585 FSB NO ACTION

FED 6000 A.T. (ME9) 3.06 Yes 3761 4568 DTN Install Service P/N 16049936 9751 9937 FSC NO ACTION

FED 6000 A.T. (ME9) 3.06 No 3771 4577 DTP Install Service P/N 16049942 9761 9943 FSD NO ACTION

FED 6000 A.T. (MD9) 3.18 Yes 8051 8145 FCN Install Service P/N 16049719 STE 0001 9720 FTK NO ACTION

FED 6000 A.T. (MD9) 2.84 Yes 3801 4614 DTT Install Service P/N 16052588 9791 2589 FSJ NO ACTION

FED 6000 A.T. (MD9) 2.84 No 3811 4620 DTU Install Service P/N 16049964 9801 9965 FSK NO ACTION

FED 6000 A.T. (MD9) 3.18 Yes 3821 4625 DTW Install Service P/N 16052594 9811 2595 FSL NO ACTION

FED 6000 A.T. (MD9) 3.18 No 3831 4636 DTX Install Service P/N 16052639 9821 2640 FSM NO ACTION

FED 6000 A.T. (ME9) 3.06 Yes 3841 4646 DTY Install Service P/N 16049647 9831 9648 FSN NO ACTION

FED 6000 A.T. (ME9) 3.06 No 3851 4787 DTZ Install Service P/N 16049653 9841 9654 FSP NO ACTION

A B C AIR SCAN TOOL PROM I.D. SALES MODEL TRANS. AXLE COND. DATA IN VEHICLE ACTION ----- ----- ------ ---- ---- ---- ---------- ------ FED Firebird A.T.(MD8) 3.42 Yes 7021 2613 CSP Install Service P/N 16049803 9441 9804 FPP NO ACTION

FED Firebird A.T.(MD8) 3.42 No 3581 4666 DSR Install Service P/N 16049838 9571 9839 FRF NO ACTION

FED Firebird A.T.(MD8) 3.45 Yes 3591 4571 DSS Install Service P/N 16049844 9581 9845 FRH NO ACTION

FED Firebird A.T.(MD8) 3.45 No 3601 4676 DST Install Service P/N 16049849 9591 9850 FRJ NO ACTION

FED Firebird M.T.(MBl) 3.42 Yes 7041 8555 CSS Install Service P/N 16052034 9461 2035 FPS NO ACTION

FED Firebird M.T.(MBl) 3.42 No 3611 8559 DSU Install Service P/N 16052056 9601 2057 FRK NO ACTION

FED Firebird M.T.(MBl) 3.45 Yes 3621 8548 DSW Install Service P/N 16052060 9611 2061 FRL NO ACTION

FED Firebird M.T.(MBl) 3.45 No 3631 8547 DSX Install Service P/N 16052065 9621 2066 FRM NO ACTION

CAL 6000 A.T.(MD9) 2.84 Yes 6971 2598 CSJ Install Service P/N 16052537 9391 2538 FPJ NO ACTION

CAL 6000 A.T.(MD9) 2.84 No 3641 4681 DSY Install Service P/N 16052547 9631 2548 FRN NO ACTION

CAL 6000 A.T.(MD9) 3.18 Yes 3651 4686 DSZ Install Service P/N 16052552 9641 2553 FRP NO ACTION

CAL 6000 A.T.(MD9) 3.18 No 3661 4691 DTA Install Service P/N 16052556 9651 2557 FRR NO ACTION

CAL 6000 A.T.(ME9) 3.06 Yes 3671 4696 DTB Install Service P/N 16049882 9661 9883 FRS NO ACTION

A B C AIR SCAN TOOL PROM I.D. SALES MODEL TRANS. AXLE COND. DATA IN VEHICLE ACTION ----- ----- ------ ---- ----- ---- ---------- ------ CAL 6000 A.T.(ME9) 3.06 No 3681 4701 DTC Install Service P/N 16049888 9671 9889 FRT NO ACTION

CAL 6000 A.T.(MD9) 3.18 Yes 8061 8151 FCP Install Service P/N 16049725 STE 0011 9726 FTL NO ACTION

CAL 6000 A.T.(MD9) 2.84 Yes 3691 4706 DTD Install Service P/N 16052562 9681 2563 FRU NO ACTION

CAL 6000 A.T.(MD9) 2.84 No 3701 4711 DTF Install Service P/N 16052566 9691 2567 FRW NO ACTION

CAL 6000 A.T.(MD9) 3.18 Yes 3711 4716 DTH Install Service P/N 16056724 9701 2725 FRX NO ACTION

CAL 6000 A.T.(MD9) 3.18 No 3721 4721 DTJ Install Service P/N 16056714 9711 6715 FRY NO ACTION

CAL 6000 A.T.(ME9) 3.06 Yes 3891 4751 DUD Install Service P/N 16049675 9881 9676 FSU NO ACTION

CAL 6000 A.T.(ME9) 3.06 No 3901 4756 DUF Install Service P/N 16049680 9891 9681 FSW NO ACTION

CAL Firebird A.T.(MD8) 3.42 Yes 7031 2618 CSR Install Service P/N 16049809 9451 9810 FPR NO ACTION

CAL Firebird A.T.(MD8) 3.42 No 3951 4777 DUM Install Service P/N 16049703 9941 9704 FTB NO ACTION

CAL Firebird A.T.(MD8) 3.45 Yes 3961 4782 DUN Install Service P/N 16049708 9951 9709 FTC NO ACTION

CAL Firebird A.T.(MD8) 3.45 Yes 3971 4792 DUP Install Service P/N 16049714 9961 9715 FTD NO ACTION

A B C AIR SCAN TOOL PROM I.D. SALES MODEL TRANS. AXLE COND. DATA IN VEHICLE ACTION ----- ----- ------ ----- ----- ---- ----------- ------ CAL Firebird M.T.(MBI) 3.42 Yes 7051 2483 CST Install Service P/N 16052038 9471 2039 FPT NO ACTION

CAL Firebird M.T.(MBl) 3.42 No 3981 8889 DUR Install Service P/N 16052074 9971 2075 FTF NO ACTION

CAL Firebird M.T.(MBl) 3.45 Yes 3991 8894 DUS Install Service P/N 16052078 9981 2078 FTH NO ACTION

CAL Firebird M.T.(MBl) 3.45 No 4001 4661 DUT Install Service P/N 16052083 9991 2084 FTJ NO ACTION

CHART II: LABOR OPERATION NUMBERS AND LABOR TIME

FOR THE FOLLOWING OPERATIONS WHICH HAVE ADDS FOR ROAD TEST AND SCOPE TEST, THESE ADDS CAN ONLY BE USED ONCE PER REPAIR.

ITEM #1 Check Engine Light (Code 34) ------------------------------------ Labor Operation Number: T1148 -- Code 34 Diagnosis Labor Time : .4 Hours (All Series) Add Road Test : .3 Hours (All Series)

ITEM #2 Engine Surge -------------------- ITEM #2A Labor Operation Number: T1149 -- Symptoms Diagnosis Labor Time : A F

.7 .6 ITEM #2B Labor Operation Number: T1150 -- PROM and/or Air Cleaner Housing - R&R or Replace. Labor Time : A F

.5 .4 Add

With A/C - - Scope Test .3 .3 Road Test .3 .3

ITEM #3 Engine Hesitation ------------------------- Labor Operation Number: T1151 -- PROM and/or Injector - R&R or Replace. Labor Time : A F

1.0 1.0

Add

With A/C - - Scope Test .3 .3 Compression Test .5 .4 Injector Harness Check With J-34730-2 .2 .2 Injector Balance Test .3 .3 Clean Injectors .8 .8

Road Test .3 .3

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.