Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 548
Symptom:
IMPROPER GEAR
When Monitored and Set Condition:
IMPROPER GEAR
When Monitored:
Engine RPM greater than 450 and output speed (ABS) greater than
180 RPM. No Input Speed sensor N2 - N3, Shift lever, and/or ABS wheel speed DTCs
present.
Set Condition:
The TCM compares the calculated gear with the gear the transmission
has actually engaged. If the actual gear differs from the gear calculated by the TCM, the
TCM value is adjusted to the engaged gear and a counter is increased by 2. If after a shift
the engaged gear and the calculated gear still match , the counter is decreased by 1 point.
A DTC is detected as soon as the counter exceeds a threshold. If the fault is detected 3
consecutive ignition cycles the transmission will be placed in Limp-in and the MIL
activated.
POSSIBLE CAUSES
ABS DTCS PRESENT
SOLENOID DTCS PRESENT
INTERNAL TRANSMISSION
TCM - IMPROPER GEAR
TEST
ACTION
APPLICABILITY
1
NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIII
t, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIII
t, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.
All
Continue
74
TRANSMISSION - NAG1
TEST
ACTION
APPLICABILITY
2
Ignition on, engine not running.
With the DRBIII
t, read Transmission DTCs.
Are there any Transmission Solenoid DTCs present?
All
Yes
→ Refer to the Transmission category and perform the appropriate
symptom.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
→ Go To 3
3
With the DRBIII
t, read ABS DTCs.
Are there any ABS DTCs present?
All
Yes
→ Refer to the ABS category and perform the appropriate symptom.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
→ Go To 4
4
Remove and inspect the Transmission Valve Body and Electrohydraulic Control Unit
Assembly per the Service Information.
NOTE: This DTC is usually set due to a internal transmission problem such
as but not limited to: stuck solenoid or valve and/or contamination in the
valve body, broken springs, leaking clutch seals, dislodged or broken snap
ring.
Inspect internal transmission per the Service Information.
Where there any problems found?
All
Yes
→ Repair internal transmission as necessary. Refer to the Service
Information for the proper repair procedure.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
→ Replace the Transmission Control Module.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
75
TRANSMISSION - NAG1
IMPROPER GEAR —
Continued
Symptom:
IMPROPER RATIO
When Monitored and Set Condition:
IMPROPER RATIO
When Monitored:
Engine rpm greater than 450 rpm, output speed greater than 180 rpm,
no N2 - N3 input speed sensor errors present, no gear selector lever errors present, no ABS
system errors, and all wheel speeds above 450 rpm.
Set Condition:
No shifting operation and detected gear is not the actual gear No shifting
operation - detected (calculated) gear is less than actual(expected) gear or no plausible gear
is calculated or Actual turbine speed - calculated turbine speed > 300 rpm or calculated
transmission ratio is above threshold. During an Upshift - detected (calculated) gear is less
than actual(expected) gear-1. During Downshift - detected (calculated) gear is less than
actual (expected) gear
POSSIBLE CAUSES
TRANSMISSION MECHANICAL PROBLEM
TCM - IMPROPER RATIO
TEST
ACTION
APPLICABILITY
1
NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIII
t, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIII
t, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.
All
Continue
76
TRANSMISSION - NAG1
TEST
ACTION
APPLICABILITY
2
Determine if there are any Transmission Mechanical problems present.
Remove the Transmission Oil Pan and inspect for debris or a plugged Transmission
Oil Filter.
Refer to the Service Information for proper removal and inspection procedures.
Is there any Debris, plugged Transmission Oil filter, or signs of an Internal
Transmission problem?
All
Yes
→ Refer to the Service Information for the proper repair procedure.
Pay particular attention to the Valve body components and stuck
solenoids.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No
→ Replace the Transmission Control Module.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
77
TRANSMISSION - NAG1
IMPROPER RATIO —
Continued
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