GM

Chevrolet | Buick | GMC| Cadillac

General Info

Powertrain

Engine

 No Spark or Weak Spark

• Very weak spark (orange spark) and sometimes no spark (2006 GMC Sierra 4.3L)
• Bad Distributor (Secondary Ignition Waveform Comparison)
  •   

Fuel Trims

• 📝 Some GM platforms will make a fuel trim active based on a “O2 Monitor : Ready” PID.

• 📝 O2 Sensor Reference Voltage Tip | 2013 Buick Verano

  • Low signal wire is not ground, it should have 1V.
  • High signal wire should have 1.7V. When you short them together, scan tool will show 0V, but voltmeter will show 1V. It is normal.
• 📎 Dirty MAF | 2000 Chevy S10

Throttle Body

• 📎 RPM Surging when A/C On | Dirty Throttle | 2004 GMC Envoy

Idle Relearn | GM

• Tip: Key ON Engine OFF. If engine will be running, procedure will not succeed (e.g. 2008 GMC Yukon)

Secondary Air Injection

📎 Secondary Air Injection, P2440 | Bad Pump | Buick LaCrosse

EGR

📝 P1404 EGR Closed Position Performance | PCM Reflash (TSB) | 2001 Chevy Impala 3.8L

Timing

• 🩺 Start and Die | CKP Gap | 2007 Chevy Uplander

• 📝 Misfire cyl. 5 & 6. P0336 | Wrong Camshaft | 2001 Chevy Camaro 5.7L

  • P0336 CKP sensor range/performance. Misfires on cyl. #5 and #6.
  • Crankshaft variation relearn cannot be completed.
  • Waveform looks good, but it turned out that the wrong crankshaft was installed. There are  two different 24X and 58X crankshafts reflectors that will fit this platform.

• Crankshaft Position Relearn (P1336)

  • P1336  Cadillac – Crankshaft Position System Variation Not Learned
  • CKP variation relearn is only there for misfire diagnosis.
  • Relearn Procedure (GM)
    • Clear all codes.
      Might need to apply parking brake and push on brake pedal before starting the car.
      When you initiate the relearn, you have to steadily raise the RPM to above 4000 (within a 10 second period).
      As soon as the RPM is high enough you will get a sharp stumble for a moment… immediately release the throttle and let the engine spin down to idle, turn key off and wait at least 15 seconds.

5V Reference

• 🩺 P0641 5V Reference 1 Circuit | 2007 Cadillac Escalade

Transmission

• TCM is inside the transmission (e.g. 2007 Yukon)
  • TCM is replaceable together with valve body (inside tranny) as one unit.
  • Required SPS Programming
  • Calibration Using Tech2Win ➱ Transmission ➱ Module Setup ➱ Clutch Calibration (?)
    • To do calibration tranny needs to be warmed to 70 degrees C.
    • If during calibration check engine comes on with “TCC Pressure Solenoid Circuit” code and tranny stops shifting completely, disconnect the battery for a min.
    • Calibration will fail if this code is current  (warm up tranny, disconnect battery to get rid of the code and do calibration again).
• TCM is a separate computer (e.g. 2003 Express)
  • TCM needs to be programmed through SPS.
    • Solenoid codes and communication codes might be present due to the lack of programming.

4WD | AWD | Transfer Case | Differential

Rear Differential Module

• Replacing Rear Differential Module requires an SPS Programming and performing a Setup function.
  • Setup function will ask for “Rank ID”, two digits, its stamped on the plastic case of one of the two connectors (smaller one) that plugs into rear differential module (aka 87).

Chassis

ABS | Traction Control

Steering Angle Sensor (Quadrature Encoder)]

• The transitions of A and B are used to determine the direction in which the shaft is being rotated. For example, a clockwise rotation would be read as going from phase 1 to 4 and a counterclockwise from 4 down to 1.
  • Clockwise (AB): LH HL HH HL
  • Counterclockwise (AB): HL HH LH LL

• Most likely these sensors don’t need to be calibrated.
• The transitions of A and B are used to determine the direction in which the shaft is being rotated. For example, a clockwise rotation would be read as going from phase 1 to 4 and a counterclockwise from 4 down to 1.
• Clockwise (AB): LH HL HH HL
• Counterclockwise (AB): HL HH LH LL

📝 Traction Light On | Difference in tire pressure | Chevrolet Impala]

• It would intermittently inform you on the dash display that the traction control was active on a normal take off from standing still, on dry pavement.
• Problem was caused by LF tire @ 26 psi, RF tire @ 79 psi

Power Steering

📎 EPS Reprogramming | Newer GM

• 17’ Equinox, 18’ Malibu, 20′ Malibu (used EPS), 14′-16′ CTS (new EPS),
  • C0565 VIN Not Plausible
  • C056e-47 ECU Software – VIN Not Programmed
• Power steering function doesn’t work. Power steering warning message and traction light are displayed.
• Live Data showed battery voltage was 0.9V with IG ON and steering angle values not changing when turning the steering wheel.
  • After reprogramming the live data started showing correct values.
• Needed SPS Reprogramming, then Configuration, and then Setup (all from same SPS menu).
• Only after performing Setup function, power steering started to work.

Suspension

• 📎 OEM Shock Absorber Bypass | 2007 Cadillac XLR

  • Installed aftermarket regular springs.
    • OEM shock absorber had a built-in solenoid. Aftermarket don’t.
  • Placed 6Ω / 50W resistor in each spring’s connector to bypass.
  • No more codes.

TPMS

• 📎 C0569 System Configuration Error | 2008 Chevy HHR
  • After reprogramming tires, perform “Tire Pressure Selection” Function

Body

ECM & Immobilizer Programming

Read more ➱ Immobilizer

Airbag System 

• • B1001 Option Configuration
    • If it’s an old car, like 2000 GMC Safari, try resetting Vehicle Antitheft System through SPS.
    • If it’s a newer car, use special functions menu in BCM or SDM to setup new SDM.
  • B0081-71 Passenger Presence System Incorrect Serial Data Received
    • 2006 Cobalt (has TSB on it). RH Seatbelt Force sensor wiring.
  • Global A (2013 Malibu)
    • Used module didn’t want to be programmed through SPS.
      • Last programming stage failed.
    • New module is programmable, but you have to select “Replace and Program” option in the beginning.
      • After programming, do a “Setup Module” through the SPS (Autel wouldn’t work).
  • 📝 Brand New SRS Module Programming | 2019 GMC Savanna
    • Needed SPS Programming to get rid of deployment loop codes.
    • Then, Autel ➱ SRS ➱ Special Function ➱ Configure New module.
      • Without performing this function, light was blinknig with no codes.

Radio & Navigation

Theft Locked (B1271)

Type 1. Global ‘A’ Vehicles (13’ Sonic, 11’ LaCrosse)

• Radios in the new Global A platforms can’t be swapped out…this is right from GM and I have run into it on an Allure, a Malibu and a Cruze. There is no way of changing the VIN in them via TIS2WEB etc.
• “Although the radio is not part of the vehicle theft prevention system, the radio does have its own theft protection. The radio theft deterrent system is intended to disable or limit radio funtionality if incorrect vehicle information is received by the radio. The radio disables functionality if the VIN information received by the radio does not match the VIN information that has been learned by the radio. A possible cause of incorrect VIN information could be that the radio was originally installed in another vehicle. The radio in Global A vehicles cannot be swapped due to the inability to alter the VIN in a radio once it has been learned.”

Type 2. MDI Unlock

• Use MDI, not AVDI.
• MDI ➱ 2006 Chevy (‘W’) Monte Carlo LTZ ➱ Body ➱ Entertainment ➱ Module Setup -> Radio (07’ GMC Yukon)
• MDI ➱ 2004 Chevy Malibu Maxx (‘Z’)  ➱ Body ➱ Entertainment ➱ Module Setup ➱ Radio (2004 Chevy Malibu Maxx)
  • Clearing VIN for Plug and Play Trick
    • The “Relearn VIN” function will wipe only the old VIN # from the radio and that long how after procedure you do not cycle you ignition off/on, the radio will not learn the new VIN. In this point radio may be disconnected and used on any another GM vehicle with matching OEM plugs. After installation to the new vehicle and on first ignition turn on radio will learn the new VIN number from the car (MHHAuto).
• No sound after unlock
  • Checked input of audio to the AMP with a little speaker, all good. Replaced AMP. Tested all speakers through AMP diagnostics. All fine.
    • AllData claims AMP has to be programmed. Programmed using SPS. Still no sound.
  • Programmed Radio using appropriate RPO’s and that fixed the sound issue.

Type 3. EEPROM Work (2003 2004 GMC Sierra)

• Read 9355093 as 24c08 (DK Link)
• At the bottom of the file (locations vary) change the VIN, only last 6 numbers.
• Popped the radio into the truck and works fine.
  • 

Battery | Charging

• 📝 No charge after 4000rpm | Wrong spark plugs
  • On 2005-2008 Corvette alternator may stop charging at 4000 rpms and above. This can be caused by racing spark plugs that induce high voltage potential to an adjacent alternator sense wire. GM doesn’t know if that situation had caused voltage regulator to be confused or it made it think that the system is overcharged causing it to logically lock-up. OEM spark plugs fixed the problem. Note: this system should not stop charging unless excitation is removed.

Seats

📎 Heated Seats Inop. | GM

• Clear codes in BCM (e.g. 2016 Tahoe)
  • Controls will also not work when engine is off.
• Clear codes in SRS (e.g. 2020 Equinox)
• Programming
  • 2018 Cadillac CT6 with brand new Right Front Short Range Module.
    • Until it was reprogrammed, heated seats wouldn’t work.
  • Service manual leads to look at the control switch states in BCM live data and if they don’t change when pressing seat heating buttons, replace control panel.
    • This is a mistake. Even when seat heating system is working properly, those control state in BCM’s live data don’t change.