CHECK ENGINE LIGHT CODE 34 DIAGNOSIS INFORMATION LISTED
Model and Year: 1985 CELEBRITY, CAVALIER & CITATION MODELS (VIN CODE W) AND 1985 CAMARO MODELS WITH LB8 2.8L MFI ENGINE (VIN CODE S)
TO: ALL CHEVROLET DEALERS
Customer comments may be received on some 1985 cars with the 2.8L MFI engine regarding check engine light (Code 34), engine surge or engine hesitation. Listed below is some 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:
o Engine running
o Mass Air Flow sensor (MAF) disconnected, faulty relay or MAF signal circuit shorted to ground.
OR
o 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 light between ground and the "+" terminal of the MAF sensor harness. With the ignition "on", the test light should light. If the light doesn't light, check for an open in the + 12 volt supply or a faulty relay.
If the 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:
o Checking rear spark plug wires for heat damaged wires. Replace if damaged.
o 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 does not go away, update of the following parts should correct the condition.
o Install the latest PROM unless the vehicle already has it. (This can be done by using Chart 1).
The latest PROM has revised EGR scheduling when the torque convertor is locked. This should reduce surge.
o If the car is a Chevrolet Celebrity, Pontiac 6000 or Pontiac STE, install a new air cleaner housing which has a honey cell flow straightener. This is provided in a service kit (Part Number 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 it should be 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 hesitations during accelerations when the engine is cold, update the following parts to correct the problem.
o Install the latest PROM unless the vehicle already has it. (This can be done using Chart I).
o If the vehicle has early production injectors, install the updated injectors which have a revised spray pattern. The updated injector is part of a kit P/N 1711297, (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 above updates, follow diagnostic procedures for hesitation in Section B-Symptoms, 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 to run this test because this test will identify plugged injectors. If the injectors are plugged clean the injectors using recommended service procedures.
Labor Operation Number: Reference Chart II. Labor Time : 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 A A.T.(MD9) 2.84 YES 6961 2412 CSH Install Service 9381 9781 FPH P/N 16049780 NO ACTION
FED A A.T.(MD9) 2.84 No 3731 4726 DTK Install Service 9721 2573 FRZ P/N 16052572 NO ACTION
FED A A.T.(MD9) 3.18 Yes 3741 4731 DTL Install Service 9731 2578 FSA P/N 16052577 NO ACTION
FED A A.T.(MD9) 3.18 No 3751 4736 DTM Install Service 9741 2585 FSB P/N 16052584 NO ACTION
FED A A.T.(ME9) 3.06 Yes 3761 4568 DTN Install Service 9751 9937 FSC P/N 16049936 NO ACTION
FED A A.T.(ME9) 3.06 No 3771 4577 DTP Install Service 9761 9943 FSD P/N 16049942 NO ACTION
FED A-POLI A.T.(MD9) --- Yes 3781 4584 DTR Install Service 9771 9948 FSF P/N 16049947 NO ACTION
FED A-POLI A.T.(MD9) --- No 3791 4603 DTS Install Service 9781 9954 FSH P/N 16049953 NO ACTION
FED A A.T.(MD9) 2.84 Yes 3801 4614 DTT Install Service 9791 2589 FSJ P/N 16052588 NO ACTION
FED A A.T.(MD9) 2.84 No 3811 4620 DTU Install Service 9801 9965 FSK P/N 16049964 NO ACTION
FED A A.T.(MD9) 3.18 Yes 3821 4625 DTW Install Service 9811 2595 FSL P/N 16052594 NO ACTION
FED A A.T.(MD9) 3.18 No 3831 4636 DTX Install Service 9821 2640 FSM P/N 16052639 NO ACTION
FED A A.T.(ME9) 3.06 Yes 3841 4646 DTY Install Service 9831 9648 FSN P/N 16049647 NO ACTION
FED A A.T.(ME9) 3.06 No 3851 4787 DTZ Install Service 9841 9654 FSP P/N 16049653 NO ACTION
FED J A.T.(MD9) 3.18 Yes 8481 2643 CXM Install Service 9481 9817 FPU P/N 16049816 NO ACTION
FED J A.T.(MD9) 3.18 No 8491 2648 CXN Install Service 9491 9823 FPW P/N 16049822 NO ACTION
FED J M4 3.65 Yes 8521 2503 CXS Install Service 9521 2044 FPZ P/N 16052043 NO ACTION
FED J M4 3.65 No 8531 2508 CXT Install Service 9531 2088 FRA P/N 16052087 NO ACTION
FED X A.T.(MD9) 2.84 Yes 6981 2603 CSK Install Service 9401 2543 FPK P/N 16052542 NO ACTION
FED X A.T.(MD9) 2.84 No 3861 4797 DUA Install Service 9851 2599 FSR P/N 16052598 NO ACTION
FED X A.T.(MD9) 3.18 Yes 3871 4741 DUB Install Service 9861 2604 FSS P/N 16052603 NO ACTION
FED X A.T.(MD9) 3.18 No 3881 4746 DUC Install Service 9871 9670 FST P/N 16049669 NO ACTION
FED F-CHV A.T.(MD8) 3.42 Yes 7021 2613 CSP Install Service 9441 9804 FPP P/N 16049803 NO ACTION
FED F-CHV A.T.(MD8) 3.42 No 3581 4666 DSR Install Service 9571 9839 FRF P/N 16049838 NO ACTION
FED F-CHV H.T.(MB1) 3.42 Yes 7041 8555 CSS Install Service 9461 2035 FPS P/N 16052034 NO ACTION
FED F-CHV M.T.(MB1) 3.42 No 3611 8559 DSU Install Service 9601 2057 FRK P/N 16052056 NO ACTION
CAL A A.T.(MD9) 2.84 Yes 6971 2598 CSJ Install Service 9391 2538 FPJ P/N 16052537 NO ACTION
CAL A A.T.(MD9) 2.84 No 3641 4681 DSY Install Service 9631 2548 FRN P/N 16052547 NO ACTION
CAL A A.T.(MD9) 3.18 Yes 3651 4686 DSZ Install Service 9641 2553 FRP P/N 16052552 NO ACTION
CAL A A.T.(MD9) 3.18 No 3661 4691 DTA Install Service 9651 2557 FRR P/N 16052556 NO ACTION
CAL A A.T.(ME9) 3.06 Yes 3671 4696 DTB Install Service 9661 9883 FRS P/N 16049882 NO ACTION
CAL A A.T.(ME9) 3.06 No 3681 4701 DTC Install Service 9671 9889 FRT P/N 16049888 NO ACTION
CAL A A.T.(MD9) 2.84 Yes 3691 4706 DTD Install Service 9681 2563 FRU P/N 16052562 NO ACTION
CAL A A.T.(MD9) 2.84 No 3701 4711 DTF Install Service 9691 2567 FRW P/N 16052566 NO ACTION
CAL A A.T.(MD9) 3.18 Yes 3711 4716 DTH Install Service 9701 2725 FRX P/N 16056724 NO ACTION
CAL A A.T.(MD9) 3.18 No 3721 4721 DTJ Install Service 9711 6715 FRY P/N 16056714 NO ACTION
CAL A A.T.(ME9) 3.06 Yes 3891 4751 DUD Install Service 9881 9676 FSU P/N 16049675 NO ACTION
CAL A A.T.(ME9) 3.06 No 3901 4756 DUF Install Service 9891 9681 FSW P/N 16049680 NO ACTION
CAL J A.T.(MD9) 3.18 Yes 8501 2653 CXP Install Service 9501 9828 FPX P/N 16049827 NO ACTION
CAL J A.T.(MD9) 3.18 No 8511 2658 CXR Install Service 9511 9834 FPY P/N 16049833 NO ACTION
CAL J M4 3.65 Yes 8541 2513 CXU Install Service 9541 2093 FRB P/N 16052092 NO ACTION
CAL J M4 3.65 No 8551 2518 CXW Install Service 9551 2048 FRC P/N 160552047 NO ACTION
CAL X A.T.(MD9) 2.84 Yes 6991 2608 CSL Install Service 9411 9798 FPL P/N 16051184 2271 1185 HHN NO ACTION
CAL X A.T.(MD9) 2.84 No 3911 4761 DUH Install Service 9901 9687 FSX P/N 16049686 NO ACTION
CAL X A.T.(MD9) 3.18 Yes 3921 4766 DUJ Install Service 9911 9693 FSY P/N 16049692 NO ACTION
CAL X A.T.(MD9) 3.18 No 3931 4771 DUK Install Service 9921 9698 FSZ P/N 16049697 NO ACTION
CAL F-CHV A.T.(MD8) 3.42 Yes 7031 2618 CSR Install Service 9451 9810 FPR P/N 16049809 NO ACTION
CAL F-CHV A.T.(MD8) 3.42 No 3951 4777 DUM Install Service 9941 9704 FTB P/N 16049703 NO ACTION
CAL F-CHV H.T.(MB1) 3.42 Yes 7051 2483 CST Install Service 9471 2039 FPT P/N 16052038 NO ACTION
CAL F-CHV H.T.(MB1) 3.42 No 3981 8889 DUR Install Service 9971 2075 FTF P/N 16052074 NO ACTION
CHART II: LABOR OPERATION NUMBERS AND LABOR TIMES ---------------------------------------------------- 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 Add : .4 hours (All Series) Road Test : .3 hours
ITEM #2 Engine Surge ----------------------------
ITEM #2A -------- Labor Operation Number: T1149 -- Symptoms Diagnosis Labor Time : ST (Straight Time)
NOTE: THIS IS A ST (STRAIGHT TIME) OPERATION WHICH REQUIRES TIME DOCUMENTATION. ZONE APPROVAL IS REQUIRED BEYOND .5 HOURS.
ITEM #2B -------- Labor operation Number: T1150 -- PROM and/or Air Cleaner Housing - R & R or replace.
Labor Time : A F J X --- --- --- --- .4 .4 .3 .3
ADD:
With A/C - - .1 - Scope Test .3 .3 .3 .3 Road Test .3 .3 .3 .3
ITEM #3 Engine Hesitation --------------------------------- Labor Operation Number: T1151 -- PROM and/or Injector- R & R or replace.
Labor Time : A F J X --- --- --- --- 1.0 1.3 1.6 1.0
ADD:
With A/C - - .1 - Scope Test .3 .3 .3 .3 Compression Test .5 .4 .4 .5 Injector Harness Check With J-34730-2 .2 .2 .2 .2 Injector Balance Test .3 .3 .3 .3 Clean Injectors .8 .8 .8 .8 Road Test .3 .3 .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.
