20 Most Recent 1999 GMC Sonoma Questions & Answers


I tried the DIY service and repair manuals from a website and it actually helped me repair transmission problem in my ford explorer. it wont move forward or
reverse, engine is good both solenoids for forward and reverse work.
I don't have much technical knowledge but I just followed it step-wise, and works perfect! got it from www.reliable-store.com

1999 GMC Sonoma | Answered on Jun 26, 2018


You will get your solution and all info on service info, repair info, parts info, wiring/electrical/fuse diagrams, error/fault codes, torque specs, PCV,

owner's/service/repair/parts/maintenance manuals etc everything
this website www.reliable-store.com
it's a very good website for vehicle problems even as old as 1991 ford..

1999 GMC Sonoma | Answered on Mar 19, 2018


I think you could use this manual method instead.. My nephew who is a full time mechanic uses it
most of the times,
and all mechanics look up to manuals. It's very easy he gets it from. www.reliable-store.com

1999 GMC Sonoma | Answered on Mar 08, 2018


My first concern is: how do you know there isn't fire? Did you
1- Check it with a screwdriver inside the spark plug wire at spark plug end to ground. This isn't the right way.
2- Have you check fire with HEI spark tester.
(The right way). To see a spark with the tester there will be 25k the spark to jump to ground and it test the coil working properly.
Now the fire system or ignition spark work this way.

When the engine is turning up to 400rpm the camshaft gear inside the engine makes distributor shaft turning. We often see the distributor gear at the end worn like an eaten apple.
Remove the Dist. Cap Somebody starts the engine look for the rotor if it turns. This will tell you the gear is OK.
P.S; What you call the SENSOR = Ignition Module just to let you know
Hope it helps

1999 GMC Sonoma | Answered on Feb 19, 2018


Common problems
1. fuel filter clog and fuel pump stop working
2. Crankshaft sensor (spark is cut during high demand)
3. Air filter clog (not enough air during high rpm
hope it helps

1999 GMC Sonoma | Answered on Feb 05, 2018


probably changed the wrong sensors
The units you should have replaced are the heated oxygen sensors in the exhaust manifold before the cat converters (HO2S)
oxygen sensors(O2S ) are after the cat converters codes p 0171,0174 are lean mixture codes and p 150,p0154 are HO2S sensor faults
as the Ho2s sensors read the composition of the exhaust gas and report to the ECM to adjust the fuel settings then t faulty HO2S sensors will result in a lean or rich reading resulting in the other codes

1999 GMC Sonoma | Answered on Jan 28, 2018


What is wrong????????? That would be a guess on anyones part here ! Testing the electrical circuits involved would be the proper way to diagnose this no start problem ! Using a volt meter an wiring diagram to check voltage at different point's in the starter circuit . voltage drop testing ! Plus knowing how the starter system works !
Starter Circuit Operation
Voltage is applied at all times to the ignition switch from the IGN A fuse through CKT 42 (RED). When the ignition switch is turned to the START position, voltage is applied to the CRANK fuse through CKT 5 (YEL). From the CRANK fuse , voltage is either applied to the clutch pedal position switch (M/T) or the park/neutral position switch (A/T) through CKT 806 (PPL). When either the clutch is disengaged (M/T) or the transmission is in park or neutral (A/T), voltage is applied to the coil of the starter relay through CKT 1035 (PPL/WHT). Since the starter relay is permanently grounded at ground G102 through CKT 150 (BLK), the starter relay energizes.
Voltage is applied at all times to the starter relay contacts from IGN A fuse through CKT 42 (RED). When the starter relay energizes, the starter relay contacts close, and voltage is applied to the starter motor solenoid. Since the starter motor solenoid is permanently case grounded, the starter motor solenoid will energize two coils. The pull-in winding coil energizes in order to pull the starter motor solenoid contacts closed. When the contacts close, a plunger on the contacts causes the pull-in winding coil circuit to open. The hold-in winding coil then holds the starter motor solenoid contacts closed. Voltage is then applied to the starter motor from the battery through CKT 1 (RED) and the closed contacts of the starter motor solenoid. Since the starter motor is also permanently case grounded, the starter motor will run until the ignition switch is moved out of the START position. When this happens, a spring in the starter motor solenoid moves the starter motor solenoid contacts and the plunger back to the rest position.


Starter Voltage Drop

How to voltage drop test starter motor circuit

1999 GMC Sonoma | Answered on Jun 23, 2017


Check the fuel injectors, with the key on one side of the two wire connector will have battery voltage, if none is present then check the ECM fuses in the underhood fuel box.

1999 GMC Sonoma | Answered on Jun 22, 2017


was the new ecm flashed to this vehicle --also what saused ecm to burn up you may have other connections --fuses--relays burnt up also need to test the obdll connector possible damage or blown fuse if the sonoma's accessory /cig lighter is out usually shares same fuse as the obdll port

1999 GMC Sonoma | Answered on Apr 18, 2017


Sounds like more than one issue, not getting as hot as before, and slow to change from vent to defrost, The first I suspect you have a thermostat failing, not a big job or expensive either, remove the thermostat putt it in an old pan full of water bring it up to a boil, with a thermometer (I use a meat thermometer from the dollar store as you won't want to use it for food again) watch at what temp the thermostat pops if it doesn't pop at around 180 then replace it.

second is the delay in switching from vent to defrost, again is not to expensive but is a bit troublesome as it sounds like you have a weak vacuum the louvers are moved by little dash pots the dash pot that moves the louver behind the dash could have a bad diaphragm or a crack vacuum line. not expensive just a pain to get at. a can of wd40 with the straw in place can help diagnose the problem if it changes properly when sprayed at time of activation (the line first then the dash pot) you will have found the bad boy Good luck

1999 GMC Sonoma | Answered on Apr 14, 2017


Is the pump getting power? Is fuel being injected? Do you have any OBD2 fault codes in memory on a fault code test from the diagnostic port under the dash?

1999 GMC Sonoma | Answered on Dec 14, 2016


The eighth digit in the vin# tells you what engine is in it. 4 cylinder or 6 cylinder. They can not be swapped.

1999 GMC Sonoma | Answered on Nov 12, 2016


There is a shifter unlock cable( not plug in or loose). The only thing with the cylinder replacement may be a relearn for security. This kills the engine, doesn't mess with the shifter or transmission.

1999 GMC Sonoma | Answered on Oct 22, 2016

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