Operation CHARM: Car repair manuals for everyone.
Home >> Oldsmobile >> 1988 >> Calais FWD L4-138 2.3L DOHC QUAD 4 >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Technical Service Bulletins >> All Technical Service Bulletins >> Engine Controls - Updated Code 26 (QDM) Chart
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Engine Controls - Updated Code 26 (QDM) Chart

89Oldsmobile10

SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E3 - DRIVEABILITY AND EMISSIONS - REVISED CODE 26 AND ADD CHART C-8D

MODELS/YEARS: 1988 CUTLASS CALAIS 2.3L (VIN CODE D)
NUMBER: 88-T-141A

CORP. REF. NO: 916512R 916516
DATE: August 1989

SECTION: 6E
This bulletin cancels and supersedes Dealer Technical Bulletin 88-T-141 which may be discarded.

This bulletin:

1. Updates Code 26 (Page 2 of 3) Facing Page "Diagnostic Aides" and Chart in Section 6E3 "Driveability and Emissions"

2. Adds Chart C-8D Facing Page and Chart in Section 6E3 "Driveablity and Emissions"

These charts should be added to the 1988 Cutlass Calais Service Manual with 2.3L "N" (VIN D) applications.






CODE 26

(Page 2 of 3)
QUAD-DRIVER (QDM) CIRCUIT

2.3L (VIN D) "N" SERIES (PORT)

Diagnostic Aids:
Intermittent open or ground in controlled circuit will cause Code 26 if present continuously for 20 seconds or longer.

Intermittent Code 26 may be caused by an improperly functioning second or third gear switch. Refer to CHART C-8D for proper gear switch operation.



CHART C-8D

TRANSMISSION GEAR SWITCHES CIRCUIT CHECK 2.3L (VIN D) "N" SERIES (PORT)
Circuit Description:
CHART C-8D is used to check the 2nd and 3rd gear switch inputs to the ECM. Transmission gear input signals to the ECM are determined as follows:

1st gear = 2nd gear switch closed
(also P/N & R) 3rd gear switch open

2nd gear = 2nd gear switch open
3rd gear switch open

3rd gear = 2nd gear switch open
3rd gear switch closed



Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. Step one checks for an open or grounded circuit between transmission connector and ECM. Since the ECM terminals are normally high, B + should be indicated at both terminals with the connector removed. A DVM must be used for this step.
2. A test light to B + is used in this step to check transmission switches for the normal state. This is 1st gear (or P/N) state. The light should be "ON" for the N.C. 2nd gear switch. Use of the wiring probe kit J 35616 will assist in this and step 3.
3. The third step checks to see if the transmission switches function normally. In third gear both switches should have changed from their original 1st gear state.

Diagnostic Aids:

A sticky or improperly functioning 2nd or 3rd gear switch may cause Code 26 to set intermittently.
pro multis · About Operation CHARM